Just a registrar?
Right now yahoo is offering $1.99 for the first year and $9.99 each additional year.
http://smallbusiness.yahoo.com/domains/?p=BESTDEAL
I've also used
http://www.namecheap.com and had great service. They are only $8.88/year.
If you are looking for a whole package I am using
http://hostnine.com/ right now. Servers are excellent!