I was pulling my hair out as well since adding three20 correctly to your new iOS4 with really basic instructions listed here: http://github.com/facebook/three20 did not work as well.
Issue: Can compile newly three20 to your iOS project and got this error: Can't find #import "Three20/Three20.h".
Here is the best solution for those have the same issue:
Add your three20 to your iphone project path like this:
[yourProjectPath]/[iOSProjectName]/three20/..
cd three20 dir
run:
python src/scripts/ttmodule.py -p [yourProjectPath]/[iOSProjectName]/[iOSProjectName].xcodeproj Three20 -c Debug -c Release
- go to XCode and do a build now.
Thanks to jverkoey for adding this in, you saved us a lot of headaches.
http://github.com/facebook/three20/commit/0814b1c149cbe987557c88a271f999c3f9f3ae64