Google has introduced a new feature for Gmail users to allow them to access their email offline. Announced on the Google blog you will be able to cache your messages on your computer using Google Gears.
A user will be able to open a browser and point it to gmail.com and have acess to their emails and be able to edit, read, and even write emails but they will not send until the user connects back to the Internet.
"Once you turn on this feature, Gmail uses Gears to download a local cache of your mail. As long as you're connected to the network, that cache is synchronized with Gmail's servers. When you lose your connection, Gmail automatically switches to offline mode, and uses the data stored on your computer's hard drive instead of the information sent across the network. You can read messages, star and label them, and do all of the things you're used to doing while reading your webmail online. Any messages you send while offline will be placed in your outbox and automatically sent the next time Gmail detects a connection. And if you're on an unreliable or slow connection (like when you're "borrowing" your neighbor's wireless), you can choose to use "flaky connection mode," which is somewhere in between: it uses the local cache as if you were disconnected, but still synchronizes your mail with the server in the background. Our goal is to provide nearly the same browser-based Gmail experience whether you're using the data cached on your computer or talking directly to the server."
The offline system is currently in beta and is available through Google Labs; it will be available to users in the US and the UK in the next couple of days.