Windows only: There are a lot of video converting programs out there, but with a few caveats, Freemake is a clean and simple one-stop-shop for all your video converting, editing, and burning needs.
Click on the screenshot to get a closer look.
While Lifehacker favorite Handbrake is, and probably will stay, king of the video programs, Freemake is an incredible alternative if you don't need a ton of control. Freemake has a simple drag-and-drop interface that allows, first and foremost, for video conversion between a ton of formats and a number of different presets for everything from iPad to PSP to HDTVs. You can also burn files to DVD, upload them to YouTube, create a photo slideshow, and even cut, rotate, and otherwise perform simple edits on it beforehand with the built-in video editor. Think Apple's iMovie + iDVD + Lifehacker favorite Handbrake rolled into one program, but about a million times easier to use.
The one downside is that you don't have nearly as much control as you do with Handbrake. For example, you don't have control over, say, converting for a constant quality level or for a 700MB output file—you're stuck with whatever it gives you. It's also worth noting that it doesn't rip encrypted DVDs—it can convert from DVD format, but you'll need to rip them with your favourite decrypting program first. For those of us that need a bit more control, Handbrake is still a better option, but for most purposes you can't beat Freemake's ease of use and still rather high flexibility.
Freemake is a free download for Windows only.