Here's a time calculator/predictor that I've been working on:
timescalculator.appspot.com
::How to use it::
Provide it with 2 times, and it will calculate all of your other times. Note that this is for SIMULTANEOUS current ability. In other words, do not expect high accuracy if the 2 times you provided were set 2 years apart.
So far, the results seem to be reasonably accurate. However, the calculator is still very much in beta/development stage.
::unfinished issues::
1) It ain't pretty. Very basic and bare webpage
2) 100m/200m results might be +/- ~.5 off
3) no error checking. If you put bogus numbers in, you will probably get bogus results (and with no warning)
4) as I'm typing this, I just noticed that it only accepts seconds (an 800m time of 2:00 should be entered as 120 not 2:00).
I'll work on those unfinished issues when I find the time (this weekend?). Otherwise, it's shown to be pretty accurate for all of the runners that I know. Check it out!