I am slowly rebuilding my projects one by one, porting them from Zope to AppEngine. I restored Chinese Radicals just now. This is a program that I wrote to teach myself to read Chinese (I didn't want to learn to write or speak it, just read). I never got around learning it of course, but strangely enough some people mailed me saying they missed the program. Hopefully it works better for you guys than for me.
Second is Google Share. I believe this is one of my earliest Google Projects and I wrote it after reading an article by Steven Berlin (now famous for Everything Bad is Good for you). It is a simple, yet attractive idea. You choose a domain, let's say [search], and a number of concepts in that domain, let's say search engines and then you measure using Google the "mind share" of those concepts in that domain.
In other words, you look how many pages that contain the word [search], also contain [google], [yahoo], [msn] or [aol]. This percentage gives you an approximation of how important these concepts are within this domain. The graph below illustrates the point for search engines:
Google Share by DouweOsinga
Interestingly enough, if you wouldn't tell people, I'm sure they'd take this graph as an representation of actual market share in the search market.