I go to www.downloads.com.
Where do you find your shareware?
I go to www.nonags.com. They pick shareware that doesn’t have annoying (nagging) popup screens nor persistent reminders to purchase.
Not shareware sites per se, but http://lifehacker.com and http://tuaw.com often post about useful little bits of software from freeware to commercial.
Shareware? I haven’t heard that word in ages. Is this 2007 or 1997? When I think of shareware, the first thing that comes to mind are mail order floppy disks and BBS downloads. Shareware is like a relic from another era just like analog modems and DOS command prompts. I think the last time I ever heard the term attached to anything was Duke Nukem 3D. 
A great one I’ve been looking at lately is The 46 Best-ever Freeware Utilities.
I think I first saw these on the Dope:
They give away a (sometimes not useful or kind of crappy, but also sometimes surprisingly worthwhile) commercial piece of software every day.
Snapfiles (formerly WebAttack)
Rather specific to audio/visual work, but very useful - the tools section at VideoHelp
But most of the time, I start with a Google search and include terms like Freeware or Open Source.
Thanks for that - I’d never heard of these - but I think it might end up being set as my home page (best way I can think of to make sure I don’t miss a good one)