People love Gmail. There are a few programs that make it better, like MailPlane, but now Google's implementing the OAuth standard, allowing developers to access your Gmail in a new way, so we'll probably see even more awesome Gmail apps.
OAuth is an industry standard allows a third party to have secure access to your info without you ever telling it your password, and, just as importantly, you can slam the door in their face whenever you want. So instead of punching in your password (which can feel icky), you're just asked by Gmail whether or not you wanna grant access to the app or service. (Google's also looking to finalising a new standard for using OAuth with IMAP/SMTP.) Twitter's been using OAuth for a while, for instance, so apps can do interesting things with your Twitter account - tweet stuff or tap its geolocation powers:
One of the first to use OAuth with Gmail, Google points out, is Syphir's SmartPush app for iPhone, which pushes Gmail to the iPhone and can be customised with all kinds of advanced filters for sorting your mail, all without ever touching your password.
A lot of current Gmail-oriented apps will probably start switching to OAuth, but more importantly, this new way to access your info and this kind of data portability should make Gmail an even bigger target for app development - since we use it everyday, we're pretty excited to see what comes out of it. [Google via ReadWriteWeb]