Edit: Added paperclip validations to photo model. Fixed a bug with the js (thanks to Kevin). Commented the js file and added all methods used by SWFUPload.
SWFUpload
SWFUpload is a small JavaScript/Flash library to get the best of both worlds. It features the great upload capabilities of Flash and the accessibility and ease of HTML/CSS.
SWFUpload is [...]

I’m not going to cover how to actually code an entire social network site in rails as all social network sites vary in their functionality (and it’ll take too long). I will cover plugins and other things you might find useful though.
Quick Start
If you don’t really want to do the coding but want to get [...]