TextMate -> Preferences -> Advanced -> Shell Variables -> + -> HOME = /Users/[insert your username here]

Once I did this the default save folder it’s using now is my Desktop. Which is much nicer than “/”

I don’t know that this is an actual fix, but it seemed to work for me. YMMV. And in case it’s not obvious don’t put “[insert your username here]” in the value, but I bet you’re smarter than that anyways 😉