So far there are ten collected editions of 100 Bullets. They are widely available to buy, work out cheaper than the original comics and are all packaged up nicely for the reader with a new cover by Dave Johnson and a little introduction from someone or other. The collected editions are:

First Shot, Last Call	Split Second Chance	Hang Up on the Hang Low	A Foregone Tomorrow	The Counterfifth Detective
Collects issues 1 to 5 & Vertigo Winter's Edge 3	Collects issues 6 to 14	Collects issues 15 to 19	Collects issues 20 to 30	Collects issues 31 to 36
100 Bullets Shot, Water Back Silencer Night	Short Con, Long Odds Day, Hour, Minute...Man The Right Ear, Left in the Cold Heartbreak, Sunnyside Up Parlez Kung Vous	Hang Up on the Hang Low Epilogue for a Road Dog	The Mimic Sell Fish and Out to Sea Red Prince Blues Mr. Branch and the Family Tree Idol Chatter ¡Contrabandolero!	The Counterfifth Detective
		Originally called 'The Charm', this collection reverted to its original moniker following its Eisner Award.

More