> Is there a place I can look to see in what release a particular
> element or attribute was added, deprecated, or removed?
Well, yes and no. Yes there is, but it's not singular, and it's not
necessarily easy. The "ReleaseNotes" directory has a list of
readily available change logs and readme files from releases as far
back as mid-2005. For the most part the editors and council have been
thorough about documenting new elements in these files.
a) it is *possible*, although unlikely, that your particular element
fell through the cracks and is not so documented, or
b) you might be interested in either P5 before 2005-06 or P1 through
If (a) seems to be the case, you can of course, perform archival
research on the open source repository P5 uses on Sourceforge.
This requires a bit of knowledge about how the Guidelines are put
together and how to use at least Sourceforge if not CVS or SVN. So if
you plan to do a lot of historical research on TEI, you should
acquire those skills. If you only want to know about a particular
element and don't already have those skills, just ask. I'd be happy
to poke around for you.
Earlier versions of the Guidelines are also readily available, but
not the revision history. I don't actually know off the top of my
head if revisions of P3 and earlier were even kept; for P4 the
revisions are in a proprietary format stored only at Oxford, and they
don't want to give it out. But again, if you're interested in a
particular element, I bet one of the Oxford TEI folks would poke
around for you.
 Use http://tei.cvs.sourceforge.net/viewvc/tei/P5/Source/ for
2005-01 to mid-2006, and
2006-05-11 to present.