2.1 Changelog:

* storyline texts for UFOpedia
* some new maps
** industrial, estate, bridge and oriental
* some new weapons
** micro shotgun, machine pistol, monomolecular blade
* new alien race (shevaar)
* a lot of new and updated models, sounds and music tracks
* multiplayer
** heavily improved multiplayer support
** masterserver
* a lot of bugfixes
* improved the engine to make it more stable and portable
* basemanagement
** implemented alien containment
** base transfers partially implemented
** finally implemented the hospital

For a full list see http://ufoai.ninex.info/wiki/index.php/Changelog/2.1