Chrome only: Chrome extension ExtensionFM automatically collects MP3s from sites you visit and adds them to a browser-based library within the extension, allowing you to find all sorts of cool, new music without cluttering up your local library until you buy them.

Before we get explaining, check out the video demo below for a quick overview of how it works.

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With all the ways you can discover music today, navigating to plain old web sites and finding plain old MP3s for download isn't exactly the most attractive option. Services like Pandora or Last.fm stream songs in another window, allowing you to decide which you like and helping you buy those you do, without wasting time downloading the ones that you don't. ExtensionFM adds similar functionality to any MP3-hosting web site, automatically creating a web-based library where you can try the music out before saving it and adding it to your desktop player.

The player is set up just like any other desktop players (e.g., iTunes), and automatically grabs MP3s from web sites you visit and adds them to the library. From that page you can listen to songs, scrobble them to Last.fm, post them to Tumblr, or buy them from Amazon MP3 when you're ready to add them to your desktop music player. No more adding songs to your library just to see if you like them—now you can quickly test music and move along, adding only what you like and leaving the rest.

Currently, the extension is in closed beta and requires an invitation code to get in. Luckily, our readers can use the code LIFEHACKER and take part—but we only have 2000 invites, so act fast if you want to try it out!