Created by Bernard Flach and Peter Overbleeke the service is called opmlmanager.com and I like it a lot.  I've had problems with Dave Winer's OPML Editor (I'm getting a fatal error, can't uninstall - I know there's a fix but I can't be rss'd to fix it all) so this simple web-based OPML editing and hosting service is just what I need right now (currently using notepad).

What I like about opmlmanager.com:

• No software to install, purely web-based
• Usable: right-click enabled, fast response, easy to 'get'
• Dead easy to create an account and start playing (less than 1 minute)
• Can import existing OPML files and can export edited files - its your data.  Example: I've exported the finished OPML file and then imported to Bloglines so I can provide a user-friendly blogroll view
• It hosts your OPML file, with easy urls (my OPML is now http://www.opmlmanager.com/opml/alexbarnett.opml) and provides stats (basic)
• Outputs OPML Validated code :-)  ...so it acts as a code cleaner too. One scenario for me is I collect RSS feeds using my aggregator and although the aggregator can export OPML (using FeedDemon) the code could be cleaner. So opmlmanager.com can do this cleansing job.
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• The file can be access without login hassles so can part of a distributed directory (such as subscription list or readinglist)
• Peter and Bernard are (I think) from the cool city Antwerp (er, that's in Belgium folks, Europe) where my wife is from and where my son was born. Antwerp has more bars-per-capita than any other place in Europe :-) Update: they're from Netherlands, but hey, that's just north of Antwerp ;-)
  

More info at Peter's post.

(more of my OPML posts or others' at Technorati: OPML)