Test 255 is the latest version. It was published late last Spring. I have not yet seen the plans for when Test 285-287 will be sunset.
As for study guides, Peter Jakab and myself are in the process (slow) of creating the corresponding Certification Guide for Test 255. We are trying to learn from the past comments from this forum to improve the usability of this next certification guide.
Gary Craig,<br />Author of <a href="http://www.amazon.com/exec/obidos/tg/detail/-/032118579X/qid=1060361076/sr=1-11/ref=sr_1_11/102-0063041-4226517?v=glance&s=books" target="_blank" rel="nofollow">Enterprise Java (tm) Programming with IBM Websphere, 2nd edition</a><br /><a href="http://www.amazon.com/exec/obidos/tg/detail/-/1931182116/qid=1060361262/sr=1-30/ref=sr_1_30/102-0063041-4226517?v=glance&s=books" target="_blank" rel="nofollow">Introduction to Web Application Development with IBM Websphere Studio (Certification Guide, Test 285)</a>