The Microsoft Language Portal now features terminology and UI strings for 20 additional Windows 7 languages:
The first 35 Windows 7 languages released in October 2009, and over 90 languages will eventually be localized for Windows 7. Every month, 4-5 new Windows 7 "Language Interface Pack" languages are released and we’ll make the terminology available for search and download on a regular basis.
The best way to get information on new releases is to subscribe to Rob Margel’s Windows blog where new Windows 7 languages are announced as they become available.
Rob's blog also contains tons of useful Windows 7 tips, news and - World Cup stuff for Windows 7!
See Rob’s blog for the install points for these languages which you can download for free on top of US Windows 7 (or on top of Spanish Windows 7 for Catalan, Basque, Galician, etc.)