IDE? SATA? Hot-swappable? 5-in-3? 4-in-3? HD coolers, active or passive? Power, active, or fault LEDs? Price range? How many hard drives?
My favorite SATA enclosure is one made by Supermicro. It holds 5 hard drives, sits in 3 5.25" bays, and requires two molex connectors for power. But at $110-140 each, they aren't cheap. Let us know what you are looking for more specifically, and we will be able to better offer suggestions.