It depends on what you are using the cat5 for. It's just cable, after all. If you are using it for ethernet, then a switch (or hub) will work as a booster. If you are using it for RS485 data, then a powered splitter. If it is RGB PWM power, I have seen some amplifiers on eBay that can regenerate those signals. If it is for balanced mic-level audio, then you need a preamp and splitter.
/mike