Google has recently released the GMail app that works on IPhone, Ipad, and IPod Touch. This is a great alternative to using Apple's Mail app, or a great way to access a second Google Email. This is a free app, and I highly recommend it.
Download from ITunes
Read More about the Google GMail app on the Google GMail Blog - http://gmailblog.blogspot.com/2011/11/introducing-gmail-app-for-iphone-ipad.html