Calibre v0.3.55 now has a Microsoft LIT to LRF converter, named, you guessed it, lit2lrf. It's a thin wrapper around html2lrf which takes care of unpacking LIT files for you.
Note that it will only work on non-DRMed files. Linux users will have to manually install
ConvertLit.
Since I don't have any LIT files at the moment, I'd appreciate some testing.
Enjoy.