Gmail's mobile application at
http://m.gmail.com should work in the browser. What I do is to create a list of my most common web applications, and then I send it to my Kindle using my Kindle email address. That way I don't have to type in the web address each time, and the passwords are often stored for an extended period too. Here are my favorite mobile apps:
mobile.nytimes.com
mobile.twitter.com
m.facebook.com
mobile.lemonde.fr
mobile.economist.com
m.verizon.net