There are tons if image effects applications out there that can add new and unusual effects to your images although few that are as cool as Q@mera.
Q@mera consists of over 150 original retro 3D effects that can be applied to both still pictures and video. There's absolutely everything here from cheesy 1980s video effects to vintage camera emulators. All images are created in high definition PNG format with alpha level channel transparency. In the free version, you can apply these effects at will although if you upgrade and get a license, you can integrate the effects into messenger clients such as Yahoo and Skype but not Adium or Gchat.
You can combine retro effects to come up with some truly original filters and images that few others will be able to recreate. However, remembering what kind of combinations you used to achieve the effect is tricky but you can use Command+B to bookmarks the complete set of settings which you've used. However, some of the effects are clearly dubious in quality - many just look like variations on colorfully pixelated effects that almost obscure the image completely.
For those of us who can't get enough of PhotoBooth, or who bought a Mac before the camera came built-in, Q@mera is still a lot of retro fun.