installing MySQL on Leopard ?

It's still unclear what you say doesn't work. "It" worked for me, but
I can tell from your blog that I did things a little differently.

First, it's worthwhile saying that what's in my /Library/Startup\
Items/ directory is MySQLCOM, which I believe was installed when I
downloaded the .dmg from the mysql folks.

The other thing I regularly do is copy from the distribution directory
the my.cnf file for small installations, then edit it to point servers
and clients not to /tmp/mysql.sock but to /var/db/mysql/mysql.sock,
which is where I prefer all my mysql stuff to sit (iirc there are
security concerns with /tmp and the .sock file). I think I add a
corresponding socket entry for each database in my app's config/
database.yml file.

So I can say that on roughly three different Leopard machines I've
pretty much just downloaded the .dmg from the good folks at mysql.org
and used their stuff.

With Leopard Server, though, all this good stuff is already there, and
setting Rails apps to be proxied by Apache is wonderfully easy.