Gmail Mobile
Now you can access your Gmail account from your mobile phone or device. Just point your phone's web browser to http://m.gmail.com. Your Gmail account stays synched, whether you access it from the web or the mobile interface. It's easy to use and it's free (but yes, your wireless plan could still charge you).

It also has these cool features:
• Automatically optimizes the interface for the phone you're using
• Opens the attachments you receive in messages, including photos, Microsoft Word documents and .pdf files
• Lets you reply by call to people whose phone numbers are in your Gmail Contacts list