a few:
I reg'd a few names at Yahoo; for FIRST TIME reg'ers the price of the first name only was $2.99, after that I think it was 9.95 for additional names (dot.coms)... awhile back so not sure now. Wasn't crazy about them as registrar, limited functions and limited free services for your reg'd name.
All domains at Godaddy (dot.coms, that is) are $8.95 + ICANN .25, last time I looked. They OFTEN have sales of 10% off everything you buy. And for each non-domain name product of theirs you buy, you can register 1 name for 1.99. In other words, if you buy some service/product for 2 or 5 dollars, you can reg a domain for 1.99. Then you'd have to buy some other product, and you'll get ANOTHER domain for 1.99. Unlimited buys.
Godaddy has great services so seem to be the most popular these days (in fact they ARE) for registrar. Some of their practices I don't like - they often have 'glitches' where you type in one thing, and lo and behold as you click out of the page that thing is gone, replaced by something more expensive. That 'glitch' actually happens quite commonly, along with other practices which seem a little hard-sell. Too many things are set up to cost you more money, and too many things seem to have some 'bugs' in them and you really have to watch what you ckick on..
But, I still recommend them the most for reliability/viability/legitimacy in the services they provide.
Also have some reg's with 1and1.com. I think they offer the best deal if money is an issue; all their dot.coms are $5.99, and that includes ICANN fee. I've heard some have problems with them, so I only reg'd a few with them to try them out. No problems yet, they have been quick, simple, painless. No hidden costs that have come to light.
FYI, they have wonderfully intuitive starter websites. I usually have a pain in the arse when using online templates to build temp sites, but the 1and1 web page builder is (for what it is) wonderfully simple, complete, versatile, I was quite impressed with its clarity. (See my 'signature' below, if you like - it's built on one of their templates while I prepare my real site... I did it in no time at all. You can tell that... but the point here is they have wonderfully user-friendly starter sites if you need one in a pinch, easy even for non-geeks, and probably the most versatile of starter pages I've seen).
Those are the only companies I've reg'd through, hope it helps.