http://MirrorChecker.com/ lets you check links from various file hosting sites. Right click a link or select an URI text and choose "Check Link with MirrorChecker" from context menu - visual example.

List of sites mirrorchecker.com supports:

Rapidshare.com
Zshare.net
Zippyshare.com
Mediafire.com
Megaupload.com
4Shared.com
Speedyshare.com
Uploading.com
Uploaded.to
Ul.to
Badongo.com
Filefront.com
Bigupload.com
Filefactory.com
Sharebigfile.com
Yousendit.com
Gigasize.com
Depositfiles.com
Hotfile.com
Sendspace.com
Megarotic.com
Letitbit.net
Netload.in
Sharebee.com
DNBShare.com


OpenURL_InNew method included; thanks jsnj for the hint

added to communication extensions, thank you matt!