Is there a way to clear every application's cache? The biggest culprit is Google Music, but I would like to clear out all of my caches fairly quickly.

If I'm using my phone as a camera, having everything cached totally eats up my SD card's storage space, so I would like to either turn down the amount of caching for Google Maps, Google Music, and a few other apps, turn up how frequently the cache is cleared, or have some way to automatically clear the caches when I want to.

If relevant, I'm running an HTC Incredible with CM7.
There are plenty of apps available that will do this. One that supports both manual and periodic cache cleaning:
1 Tap Cleaner

1-Tap to clean all cache, search histories and calls log. A default cleaner is also included.
Are you running out of application storage?
You now can get more available storage space by clearing apps created cache/data files.