Easy enough to fix, just put a symlink in:

yacht:~ dbs$ cd /usr/local
yacht:local dbs$ ls -ldt mysql*
drwxr-xr-x 17 root wheel 578 Sep 1 00:31 mysql-5.1.37-osx10.5-x86_64
yacht:local dbs$ sudo ln -s mysql-5.1.37-osx10.5-x86_64/ mysql
yacht:local dbs$ ls -ldt mysql*
lrwxr-xr-x 1 root wheel 28 Sep 2 12:52 mysql -> mysql-5.1.37-osx10.5-x86_64/
drwxr-xr-x 17 root wheel 578 Sep 1 00:31 mysql-5.1.37-osx10.5-x86_64

Credit for this tip:
http://planet-geek.com/archives/2009/09/osx-snow-leopar.html