Music tagging software Shazam has been updated to v2.2. Now including full support for Mango, with fast-app switching and live tile support, you'll never need wonder what that song is you are hearing as you walk down the street. Hold up your phone, run the "tag this" function, and you'll get the answer in moments. Throw in links to the Zune music marketplace, recommendations, and YouTube links - Shazam is your gateway to "what is that tune playing in the pub?"
The free application ('Shazam') is limited to just five tags (the process of asking what this track is), before you are asked to upgrade to the Encore edition. This has unlimited tagging as well as the recommendation engine. I think five is a little bit limiting for a trial version, but Shazam has been around for some time and is cross-platform, so I suspect this is the sweet spot for conversions to the paid app.
If you have Bing Music Search available in your region, you'll already have the tagging functionality, but Shazam is worth a look for the rest of the suite - the YouTube linking is a nice touch.