Flipshare - designed to work with 'Flip video cameras, simpe editing and free to download.
iMovie for iPad and iPhone - simple of use very cheap and works well with videos filmed on an iPad or iPhone
Studio Pinnicle for iPad - simple to use more comprhensive editing abilites than iMovie, costs £8
Windows Movie Maker - windows only, simple to use, but limited editing capabilities.
iMovie for Mac - free with all new Mac computers, advanced editing features, but mac only.
Adobe Premiere Elements - PC or Mac verisons avialable, advanced editing features, costs £78.