ArchView can open archive files online without downloading the whole archive, just like normal Web pages. It is very fast since it just fetches a small portion of the archive file from the server. It supports RAR and ZIP formats, and HTTP, FTP, and file: protocols. It can present XUL or HTML interface.
The Jumplink extension for Mozilla/Firefox allows you to skip through redirect links and jump directly to the target link. This is especially useful within Hotmail messages, where all links are opened in a frame displaying at the top the useless "Close this window to return to Hotmail". When right-clicking on a link, the Jumplink extension will attempt to determine if it is a redirect link and display menu entries which let you jump through the redirection.
The Copy URL+ extension for Firefox and Mozilla makes it possible to copy the current document's address to the clipboard along with additional information such as the document's title, the current selection, or both. This behavior could be useful when you want to send an interesting link to a friend by IM or email and out of laziness don't want to copy the parts individually.