While nothing can replace the movie-theater experience -- the big screen, the crowd, the buttery popcorn -- nowadays the convenience of watching movies online at your own pace and from the comfort of your own computer screen comes a close second. With video content expanding on the web, finding quality versions of popular movies for free online -- and legally -- can be tricky. So many sites promise "free" video but don't deliver, leaving the user stuck on confusing, messy, ad-heavy sites. We've cut through the clutter and compiled six key sites for finding free movies online.