In Leopard, Tab completion in bash doesn't immediately append trailing slashes to symbolic links that point to directories. When I complained about this change to Apple, I was told it was user configurable, and I should just configure the old behavior. It took me a while to actually find the solution -- partially because it isn't within bash itself, and partially because it was quite a nuisance but not a serious problem.

For example, ~/www is a symlink to /Volumes/www, and I cd to directories below it quite frequently. I'm in the habit of typing "cd w[Tab]/pu[Tab]", which should expand to "cd www/public_html". This broke in Leopard -- I needed an extra Tab to get the / -- otherwise I'd end up with the ugly and non-functional "cd wwwpu". Anyway, the fix is:

echo "set mark-symlinked-directories on" >> ~/.inputrc

Now Tab completion works the way I want it to again. Thanks, stylishpants!