If the font EULA permits it, I would recommend TransType
http://www.fontlab.com/font-converter/transtype/

You could also try Crossfont:
http://www.asy.com/scrcf.htm
(Be aware that you cannot simply copy a Mac OS Classic font to Windows. The resource fork will get lost.)

Hmm, it doesn't look like TransType will work on OSX Lion, and Crossfont is only for PC.

Any other ideas?

I think FontForge can do it and pour you a cuppa.

Crossfont handles archived or binhexed fonts containing the resource fork. More explanation here: http://www.asy.com/helpcf.htm#copymac

There's also FontXChange for Mac, which is an Intel app so should run on Lion: http://www.fontgear.net/fontxchange.html

FontForge is certainly capable, though perhaps a bit less straightforward— you'll probably want to consult Google:
http://www.google.com/search?q=fontforge+convert+mac+pc

For any cross-environment migration or conversion, font-related or otherwise, I've always recommended doing the conversion on the TARGET system, if possible. The big advantage is that you can immediately test the result.