How to import a varbinary(max) column with bulk import?
A varbinary value is of the form 0x01020304 for SQL Server to read.

So your CSV would be

col1,col2,varbinary
foo,1,0x01020304
bar,2,0x988776655443


Edit May 2013, 

After testing, I can't get this to work with BULK INSERT with or without a format file.

I will post something more when I get it working. I can't delete this answer