The U.S. Census Bureau has recently released the first two major sets of data from the 2000 Census: Redistricting and the "Short Form" (SF1).

GeoLytics offers these products in two easy-to-use formats either at the Block level or at the Block Group level and larger geographies. The data has been compressed so that it generally fits on 1 disk and it comes with built-in mapping capabilities, based upon the new Census 2000 boundaries. With a few quick keystrokes you can generate full-blown maps or tables. You can also export the data into a statistical software package, mapping or other software package.

CensuSmart - Includes all four of the data sets described below. This is their "bundled" product which includes a copy of each of the data sets (Short Form, Short Form Blocks, Redistricting, Redistricting Blocks).
Cost: $995 (all four items purchased separately would be $2280)
http://www.uscensus.info/census2000.htm

CensusCD 2000 / Short Form - Includes all of the data released by the U.S. Census Bureau from the SHORT FORM, including 3,000 variables at the BLOCK GROUP level and 8,000 variables at the TRACT Level and above. The program also includes Zip Code Tabulation Arrays offered by the Census Bureau.
Cost: $695
http://www.uscensus.info/census2000.htm

CensusCD 2000 / Short Form BLOCKS - Includes all of the data released by the U.S. Census Bureau from the SHORT FORM at the BLOCK level, all 8+ million of them.
Cost $595
http://www.uscensus.info/census2000.htm

CensusCD 2000 / Redistricting - It has the complete Census 2000 redistricting data along with 1990 redistricting data (for easy timeline comparisons). Included with the data sets are the 1990 and 2000 mapping boundaries for 19 levels of geography: United States, Region, Division, State, County, Tract, Block Group, MSA/CMSA, PMSA, Indian Reservation & Trust lands, MCD/CCD, Place, Elementary Schools, Secondary Schools, Unified Schools, 106th Congressional, State Legislative Districts Upper, State Legislative Districts Lower and Voter Districts.
Cost: $395
http://www.uscensus.info/census2000.htm

CensusCD 2000 / Redistricting BLOCKS - Includes all of the Redistricting data released at the BLOCK level, all 8+ million of them.
Cost: $595
http://www.uscensus.info/census2000.htm

Produce packages for the 1970, 1980 and 1990 Census are also available: http://www.uscensus.info/CensusCD708090/census708090.htm as well as a 40 Year (1970, 1980, 1990 and 2000) Tract data product. http://www.uscensus.info/CensusCD40Years/censuscd40.htm