Hi,
I tend to use opto-isolators because of their ease of use and fairly low price (obviosuly depending on what performance you need). They also require a bit of current which inherntly makes them less sensitive to noise being picked up by long cables etc. TCMT4100/4600, LTV847/844 etc in SO16 package are my usual goto-parts. The PS2841 gives you four channels in a little 12-pin BSOP package - good looking device that - just stumbled across it.

As I was looking around I found the ISO1I881T which claims to be an Isolated 8 Channel Digital Input with IEC61131-2 Type 1/2/3 Characteristics. I haven't looked at the details but might be worth to take a look at. Not cheap though...

Let me know if you find anything suitable!

/Henrik.