We are currently publishing a Web Coverage Service with NDVI data covering Alaska derived from MODIS data and provided as weekly datasets. Currently we are providing data for 2000 to 2010.
This service uses eMODIS data courtesy of USGS: eMODIS: A User-Friendly Data Source By Calli Jenkerson, Thomas Maiersperger, and Gail Schmidt .
For information on how to access the MODIS NDVI Services please see our technical documentation
Additional information about MODIS derived NDVI metrics can be found here