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.