This should be in off-topic, but what the heck...
Outpost used to be VERY good if you needed something in a hurry. Their price would usually be a couple bucks higher than the going rate (and sometimes 5-10% higher than the best price on the Net), but their customer service was great, and their free overnight shipping policy was incredible. Outpost will be missed.
Onvia used to be good for the same reason. Shipping wasn't as fast, but it WAS free, and the prices were along the lines of buy.com. No more.
Buy.com often has the best price on the Net, and the $10 off $30 and $30 off $150 coupons are still reasonably available if you are not in a hurry. If I want something CHEAP, I'm not in a hurry, and it isn't the end of the world if it NEVER ships, I still usually go there. Just NEVER EVER order ANYTHING that is not "ships in 24-48 hours", as you will be very sorry.
Comp-U-Plus usually beats even buy.com by a buck or two, but their customer service is TERRIBLE, and on something small like a modem or video card, shipping can cost 30-50% of what the item costs (READ: they make ALL of their money on the shipping and "handling"

. I ordered from them ONCE, and got 1 out of 3 items broken, and WAY overcharged for shipping. I now prefer to shop elsewhere rather than get "handled" by comp-u-plus.
OD B&M has OK prices, and really good customer service. I shop there if I actually need office supplies, but for bargains, they are not what they used to be.
Staples: I won't go there. You all know what Staples is, and if you don't, you should by now.
The managers in the OMAX where I shop have not been the most customer focused, but they can still be counted on for an occasional clearance or rebate bargain. The clerks in OMAX are cool though. A couple months ago, an OMAX clerk went out of his way to find me a clearance item, and had it shipped in from another state for FREE, so I suppose you have good and bad at every store.
Just opinions. Feel free to disagree. This really should be moved to OT, but it is fun to discuss once in a while...
Nack