Find Shared Folders is a small utility which can determine which folders are shared on the network. All you have to do is to need to enter the IP Range and it will find shared folder(s) of all computers inside this range.
Update: AddictiveTips recommends giving Network Scanner a shot. It is a complete network scanning tool that is both advanced, easy-to-use, and free.
It can also find hidden shared folders(special shared folders) and has an additional option to scan one host only for faster search. A great little app for network administrators who need to check the shared folders across all the computers on a small office/home network.
Sadly this tool is not portable and needs to be installed on the system.
It works on Windows XP, Windows Vista, Windows 2003/2008 Server, and Windows 7.