The latest beta of MarsEdit includes Edit with Textmate support:
This is just a small update, an internal-only build, mainly for people who want to use TextMate.
Other changes -- customizable ping list and Markdown preview support -- are still en route, they're just not ready yet.
Changes:
*** Edit with TextMate
Edit with TextMate now appears in the File. ctrl-cmd-J. The feature requires TextMate 1.0.2b3 or better.
There appears to be a TextMate bug regarding character encoding. I use the exact same code for TextMate as for BBEdit and SubEthaEdit -- but TextMate turns curly quotes (and so on) into weird characters. Either there's something I need to set in TextMate (that I couldn't find) or there's a TextMate bug. If someone who's in touch with the TextMate folks want to get the skinny on this, that would be appreciated.