I use fabulous.com mostly, they have the cheapest rates around and since I have over 1000 domains there even little differences make a difference.
Also using namecheap, godaddy, mydomain, enom, moniker, dotster, and a bunch of others.
Either of these is fine, BUT don't register domains with your hosting company (you know when they give a free domain with hosting plan) and don't use 3rd party registrar.
1and1 are the worst, but netsol compete hard. IN fact netsol is not only crappy, but also expensive.