This site is built by Mark Ng. Adam Mills provided a logo and some design direction.
I built it because I had a desire to see who had marked my tweets as favourites. I then realised that with that information I could do much more interesting things with the information I was gathering to do that.
If you want access to the information I'm using to create this site, there is a simple API documented here.
Half way through building this, I discovered favrd and favotter, which do similar things, but in different ways. You might want to look at those, too.
I'll be adding features on to this as I go along, as time permits.
I've noticed quite a lot of japanese content via the spider. I'd be tempted to provide a japanese version of the site if someone would provide me with some translations. If you're that person, let me know by emailing me at twitfave@markng.co.uk.
This site is built using the django framework and is hosted at slicehost. Thanks to the guys at twitter for whitelisting twitfave - there's no way I could gain enough information for it to be useful otherwise.
If you have any suggestions, or find any bugs in twitfave, you can get satisfaction here (though this is a toy side project, and thus I might take some time to respond.)
You can also follow us on twitter @twitfave.