I know, it's a dumb question.
No offense intended, but if you know it's a dumb question, why not use the search function...and not ask a dumb question?
Just a (dumb) question
Anyone know of a picture of all rounds any where on the 'net (showing different calibers)?
Now for your question, yes you can shoot 38 special rounds through your 357, as a matter of fact I highly suggest you do so for practice. They are much cheaper and less recoil than the magnums. It is still a good idea to shoot the magnums some especially if you are going to depend on the magnums for personal protection.
Darth, it would be a very good idea to get some 38 special standard loads to shoot in your 357. The lighter recoil will allow you to get used to the trigger and practice your form much easier than 357 magnum loads. If you can find them, buy some wadcutters. They are designed for target shooting and are loaded very mild. Work your way up from there. Just make sure you clean the chambers on your cylinder as they will get dirtier than they will if you stick to the 357 round.
Try here http://en.wikipedia.org/wiki/List_of_handgun_cartridges
This doesn't show ALL cartridges, for example, the .45 colt is conspicuous by its absence. It does manage to get a fairly representative showing, however.