I & my colleagues store our .Net project using
dropbox but it is very ugly to see the 'obj'/'bin' folder also sync to the internet.
We need to get rid of those folder when sync. How can we do that?
So you're still syncing everything to your Dropbox account but you can select what you sync "back" to your computer(s)
There'a nice walkthrough with screenshots at How-to Geek