I haven't actually used any filters besides the ones that come in PhotoShop; any handy ones that people here on the forums can recommend?

Thanks!

Depends on what you want them for.

There are tons of specialized ones these days.

For photography in general I'd highly recommend Which emulates a lot of filters (be it color, neutral density) and old style 35mm film effects. It also has some fantastic light effects you can use (such as soft gold reflector, etc.) in post but looks as if you actually used them on location. (Note: Version 3.0 has been released, but I do not have that yet).

And the best noise reduction software I've ever used... Noise Ninja by .

For artistic effects you might try some of the filters from Alien Skin software.

Most, if not all of these listed above have trial versions or web-examples of the effects.
~Floyd

here are the ones I use
http://www.gomedia.us/arsenal/index.php
they are not free, but they are royalty free so you can use them how you like.
I also use all of the Alien Skin software.