I don't know if this is painfully obvious to everyone else, but on the off chance, I'm posting a solution to a frequent problem I experience. There doesn't seem to be an exact counterpart in OS X for Windows' SubRip, or the VobSub Resync capability for OCR recognition of VobSub video subtitles, and I hate booting into Windows (or even Parallels) just for this five-minute job.
There is D-Subtitler, though, which does extract text-based, SubRip-type subtitles from a ripped VIDEO_TS folder or subtitle-carrying .vob. By changing the file extension of the .sub portion of your VobSub subtitle set (.sub/.idx) to .vob, you can then drag that new .vob file onto the window for recognition by D-Subtitler, which then functions as normal, generating a SubRip-type text file with the extension .srt.
Hope this helps somebody...
[robg adds: I do so little with DVDs and subtitles that I wouldn't even know where to start testing this hint...but hopefully it works for those who do this sort of thing regularly.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090801132811777