Uploading from CS3 Bridge is a snap.  You can use the Simple Uploader on SmugMug itself, and drag jpgs directly from Bridge, to the uploader.  Or..... you can upload directly from within Bridge

First, open CS3 Bridge.  Then Click Tools>Photoshop Services>Automatically check for services.  If you don't see the Photoshop Services option, open your Bridge CS3 Preferences, then highlight "Startup Scripts".  You should see a checkbox that says "Photoshop Services".  Check this box, click Ok, then restart Bridge.

 
 
After that is complete, you'll see in your Tools>Photoshop Services>Online Portfolios and Galleries>Publish Photos with SmugMug...
 
Now you are ready... highlight a photo or photos in Bridge, then clic Publish Photos with SmugMug...
 
You will get a login screen:

 
Log in, and then you will see your galleries, you can choose an existing gallery or make a new one.   That's it!