A majority of tutorials online are for CS3 still since many haven't converted yet. If you're looking for tutorials on how to use the new features of CS4 that's one this, but if you're looking for just generally good tutorials, don't limit yourself by searching for CS4 only. A lot of things you do the same way in CS4 as you would in CS3. In any case, here are my photoshop bookmarks.
http://www.photoshoplady.com/
http://www.good-tutorials.com/tutorials/photoshop
http://www.photoshopstar.com/
http://www.planetphotoshop.com/
http://psd.tutsplus.com/
http://www.layersmagazine.com/category/tutorials/photoshop
http://www.dennisplucinik.com/blog/2007/08/28/60-advanced-adobe-photoshop-tutorials/
http://www.worth1000.com/tutorials
http://www.smashingmagazine.com/2008/07/15/70-beauty-retouching-photoshop-tutorials/
http://www.photoshoproadmap.com/Photoshop-blog/2008/01/16/70-horror-blood-and-gore-photoshop-effects-and-brushes/