If the source data isn't too "wide", BCP would work quite well, but I'd recommend using SSIS so you can take more advantage of simultaneous/parallel threads
Take a quick look through these great articles:
Optimizing Bulk Import Performance
http://msdn.microsoft.com/en-us/library/ms190421(v=sql.105).aspx
The Data Loading Performance Guide
http://technet.microsoft.com/en-us/library/dd425070(SQL.100).aspx
We Loaded 1TB in 30 Minutes with SSIS, and So Can You
http://msdn.microsoft.com/en-us/library/dd537533(v=sql.100).aspx
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