The tool I've heard of before was called
Bitcoin Off-The-Grid, though I think there may be others now.
There's also
vanitygen, which I've found useful occasionally just running "vanitygen 1" to get a random private key with associated address, but that doesn't help you if you have a private key already.
Edit: Oh, and I can't believe I forgot
pywallet. That may be what you're really looking for. Just as a disclaimer, the only one of these I've used personally is vanitygen; but I just haven't needed the others yet.