It depends on what exactly you mean by 3-d text. Your best bet is to do a google search on "photoshop 3-d text tutorial". Once you find something, if you need help, by all means come back and ask. You can post a pic of an image on the web, tell us a link, and you’ll probably get help on how it was created.
Well, the Extrude example is a photoshop tutorial. So… you’re in luck! You found it!
For the other one, it’s unclear which image, but if you mean the Photoshop Guru’s logo, yes, it can be done with layer styles.