there's alot
just google for sig tuts and when you find one you like, bookmark them

but theres some at
http://www.trap17.com/forums/tutorials-f205.html

http://www.tutorialized.com/tutorials/Photoshop/1

http://tutorialoutpost.com/count/3069

many more that i forgot to bookmark, and there's some great video tutorials at youtube

and also if you didn't know you may want to go to deviantart.com and look for some good brushes

here's some good ones
http://j-a-s-h-i-n.deviantart.com/gallery/resources/applications/psbrushes/          (I like 14)

http://keren-r.deviantart.com/gallery/resources/applications/psbrushes/         some good grunge brushes, i use a lot of the grunge ones

http://vveazel.deviantart.com/gallery/resources/applications/psbrushes/          and these are good too, i use 4 but havent tried any others