EDIT 5/4/10: Added some links.
The Android Market by doubleTwist lets you search the Android Market on your computer. Also has Featured, Top Paid, and Top Free app categories to browse.
AppBrain is another web front-end to the Android Market that features some junk app filtering. Install the AppBrain app on your Android device, then you can browse AppBrain's website and queue up apps for installation on your phone. Very nice! Also lets you search and browse the Android Market and features top apps in different categories.
AppAware shows you what Android users (who have the AppAware app installed on their device) are installing and uninstalling. Also has stats on the top installed/updated/etc. apps available through the web. The app also lets you show what apps people near you are installing/uninstalling.
I know we have a thread for Android discussion, but that thread has covered everything.
As a soon-to-be Nexus One owner, I'm looking for Android app recommendations from other Goodjers, and I'm sure other future Android users will appreciate an easier thread to browse for app recommendations rather than digging through the Android catch-all thread.
I'll throw in Locale, which I know somebody posted in the other thread. From their site:
With Locale, you create situations specifying conditions under which your phone's settings should change.
The only thing I remember seeing about this app is that it uses up your battery rather faster.