Flock's set to release its first big update since going 1.0 back in November (note: you can download that version here). The new version (1.1) will feature a handful of useful updates to some of the built-in services, along with integration for Web mail and Google's Picasa.
Between the two, I'm most interested in Web mail integration. For folks who aren't using a software e-mail client like Outlook, Thunderbird, or Apple Mail, the only other options are to keep a browser tab open and keep an eye on things or use a standalone software notifier or extension to let you check when you've got new messages. Flock's simply built one into the existing controls.
The new mail button links up to your Gmail or Yahoo mail account. Once you've logged in with your credentials, it'll check for new mail every few minutes and let you know when there's a new message by adding an orange spot. When you've got a new e-mail, simply clicking on the mail button will give you a list of your latest messages, complete with subject and sender. Ideally I'd like to more of a graphical indication than a little orange dot, but the functionality works fine once you get used to looking there for updates. I'd also like to see Flock provide a workaround for people who want to have multiple Gmail accounts open on the same browser, which is still limited to either one Yahoo or Gmail account at a time.
The other new and big ticket item is the integration with Picasa. When viewing Picasa Web albums, they'll show up in your media browser. You'll also be able to upload photos through Flock's specialized photo uploader just like you would for Flickr, Photobucket, and others. This certainly isn't groundbreaking, but if you're sick of having another software uploader installed for an online photo sharing service, Flock is slowly cutting away at that need.
Flock is rolling out 1.1 to current Flock users within the next two weeks.