Cyclone III with 5v inputs

Well, the DE0 is intended to be a cheap board, so I guess they lopped those off - sorry for the confusion. I would suggest IDT Quickswitches over the 245 parts, though. Quickswitches have a much lower propagation time, and are inherently bi-directional - which means you don't have to reserve a signal to switch direction. They are essentially an array of FETs operating in the linear region, so they dynamically adjust their resistance with voltage. You do still get an "output enable" if needed (usually used for hot-swapping). The only downside is that they require a fairly odd voltage to operate on, 4.3V (Vccio + 1V); but as it happens, it's easily obtainable with a standard 1N4148 diode and a 10k resistor due to the low current requirements of the part. I've used them on boards in the past, and they really do a fine job. I'm using a few octal parts on a board I'm working on now, but I saw data sheets for a 20-channel part as well.