I have used a ASUS USB Slim Blu Ray Writer (SBW-06C1S-U)
on a Mac Mini when running OSX snow leapoard. I didn't try playing any blu rays; at least none that I remember. I was able to access DVD discs. It does work with blu rays running Windows 7. It's no longer available on Amazon, but I think ASUS has updated to a new model. Like the above post, this one requires two USB ports to run. It'll working fine with one if running DVD or just ripping blu ray, but won't play a blu disc directly.
It doesn't come with any software, and I'm only aware of one software package that plays blu ray in OSX. I don't remember it's name, but it was a mediocre expereince compared to the Windows counterparts such as PowerDVD, TMT, and so forth. Although, I have read it can done through VLC, but was quite user unfriendly.
I normally run Windows 7. I was having HDD problems, and switched to OSX briefly. I used the drive to run the OSX install dics. I think I may have played a DVD movie as well.