I remembered sometime last year I was on a Europe trip and needed to check my Gmail once in a while using my O2 XDA IIi PDA.
The PDA screen is too small to be using the normal Gmail web interface. So I searched around and found Gmail Lite. It’s open source, and to be honest, it’s quite problematic.
Gmail is still in beta and is always in constant revision. So there will be updates here and there and resulting Gmail Lite unable to use until the author or someone fix it to be compatible.

Now, Gmail has finally came out with their own Gmail mobile which you can use your browser on your PDA or mobile to check your Gmail if you have wireless internet access.
Gmail Mobile PDA

Gmail Mobile offers a number of cool features:
• The interface is automatically optimized for the phone you’re using
• You can access attachments, including photos, Microsoft Word documents, and .pdf files
• If you enter phone numbers in your Gmail Contacts list, you can reply to messages by call

Google doesn’t charge you to access your Gmail account from a mobile phone, but depending on your service plan, you may be charged by your wireless provider. Check with your provider for more information about fees associated with accessing the Internet from your mobile phone.

Just enter http://m.gmail.com in your phone’s web browser to log in to your Gmail account.