It's hard not to praise Dropbox at every opportunity. I've used it for 2 years, and to me it's the best thing since sliced bread.
I use it all day every day, every time I need to share a photo, document, or need to set up locators for a mod, sign, or music for a tm track. It's indispensable. At this point I'd be lost without it.
Just a note though. You don't upload the .loc file. You upload the zip, gbx, etc. The .loc is just a text file with a URL on the first line... to where the zip, gbx, etc. can be downloaded. That's where Dropbox comes in, because you can set up direct links in it by dropping your zip, gbx, etc. into the "public" folder, right clicking on the file, choosing "dropbox" from the contextual menu and then "copy public link". Then just paste that into the top line of your .loc file, voila!