I swear I've seen a web app like this, but can’t remember its name:
I'd love to be able to log certain aspects of my life, such as glasses of water consumed in a day, number of dirty dishes at the end of the day, or whatever else, and then have the data presented and charted for me nicely (i.e. something a bit better than spreadsheets).
Bonus points for being able to handle more than just a bunch of numbers every day, such as allowing me to keep a list of bands I've seen live, number of times seen each, etc.
I know all this sounds absurdly broad, but seriously, I did see a web service along these lines a year or two ago.