COLUMNSTORE indexes is one of the new features of SQL Denali which is currently in CTP3 and available for public consumption.
COLUMNSTORE indexes are nonclustered indexes store data in a column by itself in its own pages, a strategy to make certain types of access to this data in an isolated environment more efficient. This cost benefit scales with massive rowcounts.
COLUMNSTORE indexes are intended for data warehouses or dedicated OLTP reporting systems, NOT traditional OLTP applications. There is staggering limitation in the use of COLUMNSTORE indexes that force your hand when considering where to use them.
COLUMNSTORE indexes make your table read-only