It's possible to access your Gmail account from many mobile devices. You need to log into your Gmail account from a web browser and enable the "POP3" option. Once this has been done, configure your mobile device as per a standard POP account - although note that SSL security is required. Here are the settings:
Username: Your gmail email address
Incoming server: pop.gmail.com
Outgoing server: smtp.gmail.com
SMTP Authentication: On
POP3 SSL: On
SMTP SSL: On
SMTP Username / password: As per Gmail username / password
Some specific information for certain devices:
Nokia 9500 / Nokia 9300: Note that you need to go to the account's 'Advanced' tab and set "incoming secure connection" to 'SSL'.
Series 60 phones (Nokia 6600, 7610, 3650, etc): Note that the built-in email application doesn't support SSL, and so it's not possible to get at your Gmail using Messaging. However, ProfiMail is available, and does support Gmail access
