Tom, Mike brought up the first question that hit my mind. What projects do you have in mind? Do you need them NOW, or just planning for future projects.
I'll offer some
personal observations:
Buy the best quality you can afford up front. Buy cheap clamps and you deal with cheap clamps that WILL fail at the worst time and frustrate you the whole time until they do. I'll be the dissenting opinion here, HF clamps are cheap and they will FAIL. If you buy the quick clamps there is NO hope for you, the "F" type clamps will eventually start slipping on you and the aluminum bar clamps will fall apart.
It is easier to spend a little up front then to buy cheap and end up replacing them with a better quality clamp anyways. You just lost the price of the cheap clamp. Replace enough and it'll add up.
I, generally, figure on a minimum of four like clamps. Whatever the type you will use them in pairs for the most part. In the smaller sizes; 4-12" you will probably needs lots...they're cheap if you shop around and watch the sales.
Don't discount the better quality Quick clamps. They are handy as all get out but sometimes are bulky and the mechanisms can get in the way. The smaller sizes are great and wish I had more. The longer ones (24" +) can get a little awkward to use, but do a great job.
I have a bunch of "F" clamps in varying sizes (lots of 4"). Quick clamps, Bessy Revos, (Jets are excellent also), aluminum beam clamps and pipe clamps.
The pipe clamps have their place. However, the longer lengths can get really heavy and awkward to use. I would stick to 1/2" for the shorter lengths and reserve the 3/4" for the 48"+ jobs. The 1/2" will have a tendency to flex at longer lengths. You'll need to learn to adapt as needed.
As for where to get them. I'm always on the lookout for sales. Home Depot has an excellent deal on small Bessy F-clamps. Two 6" and two 12" for the price of two individual 12" clamps. That's two free 6" clamps. Watch the sales at the holidays and the weekly fliers. Like Mike I bought 4 50" Revo K's from Lowe's when they clearanced them. I have never found them that cheap again. I, also, bought band clamps, etc.
Bottom line, always be on the lookout for the sales and buy them even if you don't need them RIGHT NOW! A clamp here, a couple there every week or so and they will add up...you'll never regret having them and you will find that you use them.
http://www.routerforums.com/attachment.php?attachmentid=283746&thumb=1
Look close...these are just the ones I use the most...