My website (http://twxlate.com) now supports Open Authentication with twitter, and it was way easier than I expected, thanks to the signpost library from Matthias Kaeppler.
It took me longer to convert the code I already had for Basic Authentication to Apache Http Components 4.x than it did to subsequently add Open Authentication support. The signpost library is well documented, and works as documented. I enthusiastically endorse it and recommend it to anyone that is looking for a Open Authentication Java library. Again, kudos to Matthias. And, a very, very big thanks! I suppose that now that the web-site could create tweets with their source listed as "twxlate" rather than "API", I'll have to actually support creating tweets and DMs. :-) Jim