Well if you get hosting or anything else non-domain related at the same time you can't really beat
www.godaddy.com $1.99 domain plus do a quick search on google for godaddy promo codes and you'll find plenty for 10% off - meaning a domain for just under a quid.
If you aren't getting anything at the time then it really depends on the extension, for example one site might be better for .com and another for .co.uk. I have been looking into a .co.uk domain for my site recently and I am currently looking at
www.1and1.co.uk it comes to £2.34 a year for a .co.uk domain with an industry standard 2 years minimum - meaning £4.68 for the 2 years.
For a .com domain I went to godaddy as I got it for $1.99 + discount however it still might be worth going there even if it is just for the domain at $8.95. (Minus any discount eg. goox3004at for $2 off or SAVETEN for 10%)
Hope that helped
