Historically, our players have always responded well to 11-man, which is essentially a continuous 3 on 2 fast break drill. The setup can be seen here: http://www.coachesclipboard.net/11ManDrill.html
To add some extra grime to the drill, we often would not limit it to one shot per possession. This tends to create some solid fights inside as well as allowing my players to learn how to finish in traffic. The downfall of this drill is it sometimes allows players to run at their own pace.
To fix the pace issue, I also sometimes run a 3-on-2 drill with a defensive trailer. It sets up similar to the 11-man I mentioned. However, instead of four lines, there are only two (on each side of half court). It works like this:
1. Players will be split into two teams. One team will form the line on one side of half court and the other team on the opposite side. Each team will also have two defenders guarding a basket.
2. Three Offensive players begin a fast break toward the two waiting defenders (beginning about 60 feet away from the rim). Once the ball crosses half court, the defending team's line (at half court) will send a player to sprint to the half court circle then become a trailing defender (the sprint to the half-court circle is to not allow the defender to recover too easily).
This creates a 3-on-2 fast break with a third defender recovering from behind. It adds a sense of urgency to the fast break drills. Offensive teams are then pressured to convert quickly and efficiently, while the trailing defender must sprint to recover.
In this case, the play continues until a defensive rebound or turnover, then the three defenders push the other way and the 3-on-2 situation repeats itself. We usually race to 21, playing by ones. The losing team must then run full-court sprints to account for the difference in scores (if they lost 21-17, they'd run four sprints).