The previous psptoolchain (1.0 series) can be accessed by:
svn export svn://svn.pspdev.org/psp/tags/psptoolchain-1.0.0
The new psptoolchain (2.0 series) can be accessed by:
svn export svn://svn.pspdev.org/psp/trunk/psptoolchain
Information on what's new can be seen in this thread:
http://forums.ps2dev.org/viewtopic.php?t=8355
Have a nice day.