There's a preview of Firmware 3.10 on the PlayStation Blog
, although you'll have to scroll down a little to find it though! It's essentially showing the Facebook integration features; which are currently limited to automatically posting events like trophies, purchases on the store etc. Finally games that support it can also post about specific events.
All 3 options can be individually turned on/off, and if you select the purchase update option, each time you download/purchase something you'll be asked if you want to post information on this purchase on Facebook. It seems to work pretty well, though of course the functionality is still limited - especially, when compared to the 360 version.
They're saying this is just the start though, so we can probably expect more features in the future. They also revamped the picture browsing to make more efficient use of the screen space. I don't think it looks great to be honest, but in terms of usability I think it's an improvement.
I'm guessing this is done in preparation for Facebook integration for pictures as well. Finally you can customise the background colour for your PSN name in the friends list, and this is then used on your friend's friends lists as well, leaving the much complained about grey only for those who are offline.