As Chris pointed out late yesterday, an official version of Gmail is now available for mobile devices with a web browser. This post offers a very brief look at what two of Google's competitors offer in terms of "official" mobile access to their mail services. Official because it's possible to read email on one of many mobile web readers from various services.
+ The Yahoo Mobile site points to this info page about they call Yahoo Mobile mail. Here we run into different services from different mobile providers. In most cases, access via a mobile web browser is available. In other cases, Sprint/Nextel for example, you also have an option to download and use a mobile client app designed for Yahoo Mail. I've been accessing Yahoo Mail from my web browser for months. I haven't tried the client app yet. The Sprint app became available in June.
+ Not being a Hotmail user it's impossible to share first-hand knowledge of what's available. However, the MSN Mobile site does offer Hotmail access. I think what's most noteworthy is that a new version of mobile Hotmail (for both the regular and mobile web are being developed/beta tested right now for the new MSN Live service. You can learn more and even catch a screenshot here and on the Your mail is here, come and get it! blog. You can also register to become a beta test of one or both services.
Postscript: P.L. points out that Google's new Gmail Mobile might not work on all phones and devices with a mobile browser. ">His comments here along with a list of phones that have been "confirmed" to work with Gmail Mobile.