Is there an online user agent database?

useragentstring.com has browser and OS information for its user agent strings. There's also an 'analyze' box to submit your own string. I don't know how easy it is to hook up to automatically, but it seems to have the sort of info you want.

Update from Original Posting (don't want to steal your upvotes):

I got this back from the author of http://useragentstring.com/:

I have a simple API, but I'm about to recode a lot of my site, so it might change in the near future. If you link to my site, you can send a useragentstring in a form field or in the querystring with the name 'uas':

http://www.useragentstring.com/?uas=Opera/9.70%20(Linux%20i686%20;%20U;%20en-us)%20Presto/2.2.0

this will automatically parse the string. if you add &getText=all

http://www.useragentstring.com/?uas=Opera/9.70%20(Linux%20i686%20;%20U;%20en-us)%20Presto/2.2.0&getText=all

you will get a text file with key value pairs like agent_type=Browser;agent_name=Opera;agent_version=9.70...

Browser Capabilities Project

The browscap.ini file is a database which provides a lot of details about browsers and their capabilities, such as name, versions, Javascript support and so on.

The browscap.ini, which provides a lot of details about browsers and their capabilities, such as name, versions, Javascript support and so on.

PHP's native get_browser() function parses this file and provides you with a complete set of information about every browser's details, But it requires the path to the browscap.ini file to be specified in the php.ini browscap directive which is flagged as PHP_INI_SYSTEM.

http://browscap.org/