The fastest way I have found to bulk load large amounts of data into mysql is this:

LOAD DATE INFILE 'file_name' INTO TABLE 'table_name';
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But this requires you to write your data into a temporary file first.
It may be possible to avoid this by using a FIFO (named pipe) on unix.

Here's a link to the mysql docs:
http://dev.mysql.com/doc/refman/5.0/en/load-data.html