I've tried MusiBrainz , but, while it works, I found it always shows all the info of the entire album/cd, while I only need the info for the track I did the search on.

BUT I've found an easier way! It's actually do-able to do batch lookups in WinAmp itself. Just put all the MP3's you want to tag into your playlist, select all you want to tag (usually ctrl-A), then right click on the files, send to: -> Auto Tag. Then a batch windows appears and all files are looked up and tagged. When all lookups have finished, you can choose to apply the changes or not...

This works wonderfully well! It also fills in the ID3v1 tags, but those are easily enough deleted all in Tag&Rename afterwards. Yay!

All I need now is a utility which can batch-tag album art as well and I'm golden! I'll have a look at MediaMonkey for this.