Well, the standalone trackback tool I posted about yesterday seems OK, and since then I've also found SimpleTracks and HaloScan.

Unfortunately, it seems that many of the trackback systems reject "trackback pings" if they don't come from the site the blog is on due to spamming. This is a bit of a shame since I can't create a trackback link from within blogger itself, and the feature wasn't added to the beta either (which is also a bit sad).

HaloScan also enables trackback functionality for your blogger blog. I won't try out the trackback functionality for now as I don't want to be a spam target myself. There's enough stupid comments that I have to moderate already and I don't want to make things worse :-)