Windows Live Movie Maker is a free download from Microsoft but only works on Vista and Windows 7.  The advantage of this software is the ease of use, you can turn home movies into youtube clips, take your family photos and turn them into a movie slideshow.  This is part of the Microsoft Live Essentials pack, which is entirely free and includes some pretty cool applications.

From Windows Live Movie Maker : Create movies and slide shows from your photos and videos, and share them with your friends and family.  Movie Maker is part of Windows Live Essentials, which includes free programs for photos, movies, instant messaging, e‑mail, blogging, family safety, and more. Get Movie Maker or get them all—they're free! Note: Windows Live Movie Maker is not available for Windows XP or earlier versions of Windows. Click the blue arrow below to begin Downloading.