I've looked around, and I can't come up with anything that offers the depth and generality of material you're looking for.
Perhaps a good idea is to use this thread to get answers from the community as you encounter concepts not well explained elsewhere.
Overall I would say a smartphone is one of those things in life best learned by jumping in and experiencing it, but there are definitely some basics that we can go over.
Prepaid/post-paid: Currently in the US there are broadly two common models for service plans used with smartphones.
The most popular currently is the post-paid contract, this is the same setup that has been used commonly for the major carriers for all types of cell phones for 20 years. You go to a carrier store(or online), you pick out a phone which will be sold at a subsidized price, you sign a contract (generally for 2 years) agreeing to a specific set of included services (voice minutes, text messaging, data, etc.) and a monthly fee. Since the phone is subsidized by the contract terms there are financial penalties for breaking the contract, and until the contract ends the phone itself is not fully yours.
The second most popular is the standard prepaid service. In this model you visit a store or go online to a service provider. In this model the provider may sell you a phone, but you will likely pay the entire cost of the device up front, and own it outright at that time. You then choose a service plan based on the same factors, you will pay the bill for the month in advance, and sign no contracts and are free to stop service at any time.
Phone unlocking: Fitting with the post paid contract model phones purchased from carriers will generally be software configured so that they can only be used on that carriers network - this is a locked phone. Unlocking then is the process of removing that software restriction so the phone can be used on another carrier. This can either be done by the carrier that sold the phone, or by a third-party process (which may be operating in a legal grey area)
Smartphone Data plans: Many of the functions that make a smartphone smart require access to the internet. This connection transmits and receives packets of data which is metered by the carrier. A smartphone service plan will include a data section that describes how you are billed for using data. The most common way this is billed is to include a pool of available data usage for each month, for instance 2GB of data transfer might be included as part of the monthly fee. Depending on the plan there may be a charge for exceeding this limit, or you may find that the speed of data is greatly reduced.
Smartphone Apps: The modern smartphone is really a computer that happens to fit in your pocket and lets you make phone calls. As with any other computer you have worked with before it is expandable through the addition of new software programs, which for smartphones have been termed Apps. Apps can perform many different functions, they can edit photos, play and even edit music and videos, create, edit and/or scan documents. There are limitations in terms of abilities on such a small device, but many things can be done.
App stores: Getting apps onto a phone is a bit different than a computer. Generally app installation is done over the internet through an app store on the phone. The store will allow you to search for apps, have recommended apps, and lists of popular apps. The store will generally bill for apps through an attached credit card handled by the company behind the store. Each smartphone system has a different choice of app store(s) and apps contained within them (much like Mac and Windows have different programs) Apple runs a store only available on iPhone (and allows no others), and Microsoft runs a similar store on WinPhone, Google runs a store for Android, which also allows for other stores to be installed, with Amazon having a popular competitive store. The base store for the phone will come installed on it, and after setting up a payment account to use with it can be used any time that network access is available.
Online/Offline: Very much like any computer program you have used before apps may work entirely on the computer/smartphone, or it may require a connection to the internet for some or all functionality. So an app that shows a map of your location (more on this in the next section) may store the maps on the phone, or may require that it connect to a server online to get the map for your area. Given that data plans (discussed above) generally allow for a limited amount of transfer in a month and may charge penalties for exceeding that limit, knowing whether an app is using online data can be important for avoiding surprise bills.
Wifi/Cell Data: Smartphones come with two primary ways to connect to the internet. Wifi is the same networking you have used on laptops for years. You open the wifi settings, pick a network you're allowed on, enter a security password as needed, and then data is sent and received through that wifi connection. Data transferred over Wifi networks does not count against your monthly data limits, so again this is useful for avoiding charges or slow speeds. The other is cellular data, this is the data covered in the service plan, this travels over the cellular provider's network. The advantage to cellular data is that it is far more available than wifi in many places, and it is seamless as you move around, meaning that you can be at home, at the office, at the dentist's and the connection will follow you without you doing anything - unlike Wifi which you need to attach to networks each time you move into a new location.
Smartphone GPS and navigation: One of the highlight features of smartphones is the ability to perform navigation services using the GPS systems for location. GPS alone would give you a longitude/latitude coordinate to tell you where you are - hardly useful for the average person who wants to know how to get to a client's office. So a smartphone will include an app (and other's could be downloaded from the store) for maps and navigation. This app will be similar to MapQuest, google maps (for android it IS google maps), and similar websites you have probably seen. The one difference is that the smartphone will use the GPS to center the map on your location and provide a dot that represents where you are. The app can be used to search for addresses, or name's of locations, or even more abstract things like "gas station" or "pizza" and will bring up a location(s) near your position that fit the search. The app will be able to give you directions for transport between your current location and a location of interest - and for the better ones this includes walking/biking, driving, and public transportation options. They will also generally be able to provide voice directions on a turn-by-turn basis to guide you as you go to your destination. (Very similar to dedicated GPS units you may have used in a car before)
Navigation and Data: Going back to the ever important data question, the mapping app can either store the map and location data on the phone or it can be stored on a server that the app communicates with at the time of use. There are advantages and disadvantages to both methods. If the maps are stored on the phone then directions and search will work even when you are out of cellular/wifi coverage, and using the maps will not be using data from your data plan. However, downloaded maps are only as current as the most recent update, and may not have as much detail about local businesses and points of interest due to space constraints. For online maps the opposite is true, without a connection to cellular or wifi the map is not able to give data, and using the map when not connected to Wifi will use data from the service plan, however online servers can be updated more frequently and will include all the data the provider has on locations.
Anyways, I do suggest simply asking more questions about terms being thrown around that lack enough explanation, I'm sure people around here would be more than happy to help bring you up to speed.
), but how can I determine which network gets better coverage in my area, T-Mobile or AT&T? I remember (it was around 10 years ago) getting a cell phone plan (my employer had provided me with a cell phone but later they changed their policy and made me buy the plan), and the carrier didn't have coverage at my house and I cancelled. Surely there are better ways to determine coverage than signing up and just experimenting! 
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