First Bonus Pack, also called Epic Bonus Pack. If you have the GOTY edition, you do not need this pack.
Included: Three new models, a package containing six related mutators, and 11 maps.

Second Bonus Pack, also called Digital Extremes pack. If you have the GOTY edition, you do not need this pack.
Included: Three new mutators and two maps.

Third Bonus Pack, also called Inoxx Map pack. If you have the GOTY edition, you do not need this pack.
Included: Two texture packs and six maps.

Fourth Bonus Pack, also called The Christmas 2000 Pack.
Included: Two new models, two texture packs and twelve new maps.