I switched to the Mac several years ago, and I'm still finding apps that have been around for a long time that I wish I had known about sooner. Hopefully the Mac App Store will help, but it also raises two issues: 1) What about apps that aren't in the store (for whatever reason, perhaps because they don't fit Apple's guidelines), and 2) How do you find apps in the Mac App Store?
Turns out that "there's an app" for the former and a website for the latter.
Regarding the issue of finding apps that aren't in the App Store: Bodega lists many apps, and it even offers deals like NetworkLocation for $14.50 (50% off today). Bodega also lets you keep a wishlist of apps,