Instructions for using Bitcoin on multiple computers / operating systems

[mcandre]

I regularly use Mac, Windows, and Linux. According to the wiki, any backup files become unsafe to use after 100 new transactions. Barring that, where is my wallet stored? I imagine C:\Users\<name>\AppData\Local\Bitcoin for Windows and ~/.bitcoin for Mac/Linux, but I'm not sure.

If I drag and drop my wallet from one OS to another, will the Bitcoin app recognize it, or is the wallet stored in a per-OS format?

[ryepdx]

I don't know the answers for sure, but seeing as nobody else has written anything...
Try searching your hard drive for wallet.dat. That'll turn up your wallet file on any OS. Finally, as far as I know wallet files are completely OS independent. I can't see any reason why they wouldn't be.

[RodeoX]

In Ubuntu it is likely  in:  /home/user/.bitcoin/