News from AllaboutSymbian, Nokia updates 5800 XpressMusic firmware from v40.0.005 to v50.0.005 today, available to most product codes.
The observed changelog is,
- Browser 7.2 (the new browser like that in the new fw of n97 has auto full screen + full kinetic scrolling + some other minor bugs fixed.)
- Lifecasting (with Maps 3.0T SR3.0)
- Flash Video Phase-3 - Flashlite 3.1.7.x
- Gimlet [...]

A new firmware for Nokia N97 is released today. The newest version is 21.0.102.
Some of this new firmware’s improvements and corrections are :-

Auto-rotate display set to ON by default.
Mass memory content updates (applies to new production only)
OviSuite 2.0 + OviPlayer installation files preloaded
Upgrade to new version of Ovi Maps (3.03) with free global lifetime navigation
Preloaded Maps [...]

NokiaN97Forum just let us know that the Nokia flag phone N97 gets a new firmware today! This update will come to all the regions until 7/2, you can check if you can update your firmware here.
Here's the official changelog from Nokia.com

Improved call reliability
Smoother touch screen scrolling
Browser improvements
Improved Music player
Improved image and video stability

And Ovi Maps 3.03 [...]

Here's the big news to all 5800XM users. Our 5800XM finally gets the new firmware v40 and the kinetic scrolling feature we have been waiting for a long time! After update, the homescreen changes to the style of 5530's which has contacts bar.
This firmware is not come to all the regions yet. If your phone [...]

Nokia N900 today gets a firmware update to 1.2009.44.1.

Here's a changelog from fonearena.com

Performance Fixes
New icons in Application Manager
Application Manager remembers the position prior to app installation( it used to go to the top on refresh before)
Red Pill mode does not work.
OVI Catalogue has been added to list of repositories
FM Transmitter Fixes

After Upgrade, the Ovi [...]

This week is really an OS week. Not long from Nokia 5800 XM and Blackberry Storm got the new firmware, Nokia releases the new firmware for N97!
The new features in the v20.0.019 are:

'flip scrolling' has been added in the entire user interface, making scrolling in all views very smooth
shortcuts to personalized homescreen
Ovi Maps 3.1 with [...]

Good news to Nokia 5800 XpressMusic users. 5800 XM gets a new firmware v31.0.101 today. You can update your phone with Nokia Software Update or FOTA. The new firmware is now available in some countries now. For other users, you have to modify your phone code to update. We strongly recommend you backup your data before any [...]

We just get news from Symbian World that Nokia  N97 has got a new firmware v12.2.024 for RM-507 currently.  But we have not got the details about this update. Some users say that after the update, it gets quicker to switch between landscape mode and normal mode; quicker to load OVI maps. You can update to [...]