AutoSilent.
Sigh, I was really looking forward to this app because I'd used similar profile schedulers on my non-iphone smartphones to switch to silent mode during work hours and back to normal after work. Then I just found out about this app, only to find it doesn't work in ios 4.
How did you determine it doesn't work on ios 4? I loaded it and the interface allows me to play with settings, but it looks like it can't actually be enabled unless I purchase the app. Did you pay for the app and it still doesn't work?