As stated in a previous post,
i-drink.com is a good place to start. I used to use that site a couple of years back. As far as "trendy" drinks go, you can really get that from a book. That's a regional thing. It can also make a diff what bars you frequent. Some bars are known for martinis, some are known for margaritas. The best thing to do is go to a bartender and ask them what their best drink is. Watch them make it to learn what's in it and try new things. Here's scarpozzi's top 3 drinks to order in bars... (keep in mind, I'm almost 23 so I've had at least 10 years of drinking experience...no joke)
1. Crown Royal and Ginger Ale - (while this sounds odd, Ginger beats coke in taste tests....it's lighter than coke and makes you beg for seconds)
2. Margarita (low salt) - These come cheap in many bars and even buy 1 get 1 at most Chilis locations in the area. Too much salt overpowers the flavor of the lime and can ruin one. Make sure the bartender knows what he/she is doing.
3. L.I.I.T. (long island iced tea) - Great drink because it can knock you down. Bartenders don't mind making this one because most use LIIT mix to save bar costs. If you ever find a bartender to make you REAL ones and charge the same amount, never leave the bar. Become a regular and hit on 21 year old chicks until you die.