As I'm working more on web applications I'm finding that there is a particular set of problems which are fixed in scope but that need constant tweaking in order to stay useful.

A possible solution for these sorts of problems might be a 3rd party online API. Here is the start of my list:

1: Email validation
2: Email verification
3: User Agent parsing

(I realize that an online API would have latency issues, but these are the sorts of things which should probably be performed asynchronously anyway)