This links to xampp works great on macs. I have put it only for PPC machines, but it claims to work properly on Intel as well.
I also had success installing FreeTDS and PHP from source on an Intel Macbook, running Mac OS 10.6 (Snow Leopard). My steps were the following:
PREPARE SOURCE CODE
step 1: download latest php version
step 2: un-tar the php source code
step 3: download latest freetds version
step 4: un-tar the freetds source code
INSTALL THE FREETDS
step 5: make sure there is a writable directory at /usr/local/freetds
step 6: "cd" to the freetds source directory
step 7: run "sudo ./configure --prefix=/usr/local/freetds --enable-msdblib"
step 8: run "sudo make"
step 9: run "sudo make install"
step 10: run "touch /usr/local/freetds/include/tds.h" (add blank, but necessary files)
step 11: run "touch /usr/local/freetds/lib/libtds.a" (add blank, but necessary files)
INSTALL THE PHP
step 11: "cd" to the php source directory
step 12: run "sudo ./configure --disable-all --with-mssql=/usr/local/freetds"
step 13: run "sudo make"
step 14: run "sudo make install"
Of course, since I was disabling-all (step 12) that means that you have to explicitly add back those modules you want to configure php with.