most info can be found at
http://www.anders.com/projects/netatalk/ and netatalk.sourceforge.net but here is the info as I have distiled it...
get netatalk 1.5.3.1 source from netatalk.sourceforge.net (under downloads) and untar and ungzip it, then (as root I think is required) cd to where it was untared and
./configure --with-shadow &&
make &&
make install
iirc that should do it, and if networking is set up correctly between the two machines e.g. the eth adapters work & are set up (not usu. a prob with the mac eh?) the linuxbox should show up in the chooser. After that, you should be able to access your home directory on the linbox via the chooser on the mac using your lin login and password.
This isn't really the perfect way, but since you're just on a simple 2 machine network etc. it should be fine for what you need.
more ?s?