MsUpload

MsUpload is an extension that makes adding files far, far easier.

Usually, to upload a file, a user has to click upload file, manually select that file, then click another tab to save the file to the wiki.

With this extension, not only can files be added as you edit, it even supports dragging files from wherever they are on your computer and dropping them in the edit window, where they will be automatically added to the wiki, and from there you can decide where and how to insert them, since this extension even has options to make that easier.