the 4 axis TB6560 driver board that is available on ebay for fairly small price (there are also variants without manual and without working video and without some cables that you get in "extras" version that cost 20+$ less !!)
The DB25 interface (parport) is standard TTL in/out so you can attach it to arduino or any other mcu, and since the inputs are going trough schmidt (74hc14) it will work both with 5V and 3v3 mcu. All inputs are also opto insulated, the stepper driver chips are mounted on cooler and all in all, even it is "classic prc manufacture", it actually works just fine. Note that "36V rating" of the board is overstatement, I heard many ppl on cnczone mention that board go in smoke if voltage used go over 24V.
The first problem I had with the board is - documentation and "real life board" does not match as DB25 (main interface) pinout from document is completely wrong. Took me more then an hour to trace manually all signals and here's the pinout so noone else need to lose time:
Apart from X stepper driver being dead on the board I purchased (I will contact seller on monday about replacement), board works very good. I was testing it with mach3 (I received mach3 with the board) on some old laptop and tomorrow I'm gonna test it with mendel but driving 3A motors I was unable to get chips to get warm , 1/16 stepping works "ok" both with fast and slow decay mode (have not tried 25/50% decay)
I know that Buzz has gotten this board going and I think he may have more info on it. I also seem to remember him saying something about putting info on the wiki (not sure if it was "have to" or "have done" though). They've got it connected to an Arduino Mega and running a Mendel (at the Brisbane Hackerspace aka HSBNE).
FWIW: They're using the Relay output to control the extruder heating element, and it works reasonably well. They're still calibrating their Mendel though, so it's not 100% operational.
I have 4 different .doc files and 2 .pdf files and every each one of them show picture of the same board but different pinout for the connectors (and none of them is same as what I posted here, what I traced on board), so I believe there are probably different revisions of the board out there that look similar but have different pinout.
The relay can take 20A on 14VDC so it is ideal for heater (I use relay instead if FET on all my printers to drive heating element).
The 4 switches on board could also be used as they are opto insulated... I tested it with mendel few moments ago and it works pretty much the same as those pololu drivers do, only this one is bit bigger, opto insulated and bit quieter (as I have to use big fan to cool those pololu's) and what is much more important, cheaper then pololus ... (50$ is the price it cost me and 4 pololu's costed me 48$ but for pololu drivers I had to add 4 big elco's, connectors, regulator and I had to put them on pcb, add some cooling ... so more the 20$ for all that, maybe even more then 30$ .. this is a ready made board with all the "features" needed to run a good printer )
From what I checked the firmware we still don't have the "panic button" implementation (a must with cnc, not so important with reprap) ... but I know there was some talk about implementing one ...
anyhow ...will see if Buzz manages to put something on wiki ... I have put this:
so hopefully he can expand it a bit with some examples and images and code
i hope that posting this will be useful. the boards require enable pin be set. if you are using mach 3, then select those pins high
also documentation on some cnc boards are on my website
as well as a beta version of firmware for arduino that has a pid control for relay. meaning that temp control is more accurate and you are less likely to burn out your nichrome. this firmware was made to connect to the cnc board mentioned above, but you can use just temp control if you want. either way, there are several documents on this page that may be useful, as well as pin out instructions.