DropBox can be a godsend, if you're careful in how you use it. For game saves where you really really do not want to mess things up, you want to set DB to use manual syncing. Automated sync can mess up your hard fought RPG grinds like you wouldn't believe if you aren't paying attention to which computer/device the file came from last.
One thing to note: If you are using any of Richard Bannister's emulators on OS X and are transferring .srm files, you need to decompress those first. They're compressed, and SNES9x will not read them until you do so (despite having .srm, they are in fact saved in .zip form, verifiable by decompressing them with Stuffit Expander).