Windows/Mac/Linux: Firefox extension Xoopit turns Gmail into a robust, searchable media management tool for every piece of media that comes through your inbox. By indexing every attachment as well as every link to photos and videos from sites like Flickr, Picasa, and YouTube, Xoopit allows you to easily search for and find any picture or video and view it from directly inside Gmail. Imagine this: You're looking for a YouTube video that you were sent a link to recently, but you really don't know where to begin your search. With Xoopit installed, you can just click the Videos tab and you'll see this:
Finding that video becomes a lot easier at this point, but you can narrow down the search even further by sorting the results, filtering by sender, or searching for the words associated with the video (even if all the original email contained was a link).
Today, Xoopit has also integrated their media search with Gmail's search box so you can get media results when you search Gmail the regular way (see their demo video for more). Once you're viewing a video or picture in Gmail using Xoopit, you can even post it to Facebook or to your blog directly from Gmail (WordPress, Blogger, TypePad, and LiveJournal are all supported).
Overall, Xoopit sounds (and is) pretty great, but there is a catch, and it's kind of a big one: You need to be willing to turn over your Gmail password to Xoopit to allow them into your inbox to index all of your email. It would be excellent to see this sort of functionality incorporated directly into Gmail so you don't need to trust a third-party with your inbox. However, if you give it a try and are unhappy with Xoopit, you can email Xoopit support and have your account deleted.
Xoopit is free, works wherever Firefox does. They're currently in a private beta, but they've promised access to Lifehacker readers who follow the signup link below. As soon as you sign up, Xoopit will start indexing your media. You should start seeing indexed content in a few minutes, and all of the media in your inbox should be indexed in under 24 hours. If you give it a try, let's hear how you like it in the comments.