On your home screen, press the menu button (bottom left corner), then settings, then select sound and notification ringtone is one of the options. If you want to use a ringtone that is not listed, open music player, find it in there and long press on it, one of the options will be set as notification ringtone. Gmail uses the general phone notification ringtone, you can't set it separately as far as i know.
You can set it separately.
Launch the GMail App > Menu Soft Key > More > Settings > Select Ringtone (it's down the bottom)
I don't see any accounts on mine. I see General Settings and Notification Settings as the titles. Maybe try going into the Inbox of a Gmail Account first, then Settings?
When I do this, I see General preferences (no ringtone option in there) and accounts. I click on my account and at the bottom is a box to turn on or off email notifications but no notification sound option.
Am I missing something??
Oops, my apologies...seems we received a sneaky update of the gmail app without being told.
Same as before, go into settings, choose the account you wish to modify settings for, and scroll to the bottom. There should be an option that reads "Labels to notify", select it. Another menu should pop up for all the folders/labels you wish to receive a notification for. Select the one you wish to edit, and in there now are the options to change ringtone, and whether or not to vibrate.
Geez...would've been nice if we'd been notified of the update...