Depends a bit on how involved you want to be in your computers security. Norton 360 (as implied by the name) claims to pretty much take care of everything. It is also a bit bloated and slow in my opinion. I'm pretty much put off by Norton, especially since finding a real good alternative at the right price, but have read good reports about all the 2009 offerings, as being much less bloated and system resource hungry.
Some names with good reputations to throw out there (not all contain the "suite-style" applications, like firewall/antispy) include Avast, Avira, Bit Defender,Bullguard, Eset (NOD 32), F-Prot, F-secure,Kaspersky, and there are plenty of others.
Any reputable AV should have a trial period. Usually between 15 and 60 days. Whatever you get, try before you buy. You have to be able to understand it, get help when needed, know if it needs a different configuration, will work when gaming etc, and after you've forked the dosh over is not a good time to discover some significant shortfall.