First get the subclipse plugin sources, and compile them, using you current SVN version. You can do it pretty easy by using the team project set [add link] and then opening the update site with the manifest editor and selecting "build all".
Pretty easy, really. Just follow the INSTALL directions in trunk (grab the APR sources, etc.).
Just don't forget to enable javahl!
Here's my config string:
./configure --prefix=/usr/local --with-openssl --with-ssl --with-zlib=/usr/include/ --with-neon=/usr/local --enable-javahl
If you didn't install neon from source, you can try the included version (although I think it's too old, even with OS X 10.5):
./configure --prefix=/usr/local --with-openssl --with-ssl --with-zlib=/usr/include/ --with-neon=/usr --enable-javahl
Then do: make make javahl make install make install-javahl
If everything went well, you can start eclipse, and update your subclipse plugin using the local update site you built earlier.
Restart and enjoy subclipse bleeding edge with SVN 1.5 bleeding edge!