Password entry on OS X and keyloggers

There's several places in my ‘personal security infrastructure’ (is there a better phrase for that?) where I find myself typing very important passwords into text-fields on OS X (for instance, dis-encrypting and mounting thumbdrives containing very sensitive data.)

I'm (perhaps unreasonably) afraid of keyloggers, as these are the only method I can think of short of a system-level vulnerability or physically watching (or recording) my activities when entering the password. In other secure systems I use, there's an option to enter a final part of the password using the mouse or similar, to help avoid keyloggers making an attacker's job too difficult.

tl;dr: Is there any way to (partially) defeat keylogger attacks against system-level password entry on OS X?