this is on my 98 3500 HD truck ... 6.5L diesel of course.
fuel is leaking from the rear of the engine, near the fuel filter housing.
fuel is puddled under the intake, but I can't see exactly where its coming from. any common leak points I need to check?

The fuel filter is not seated or tightened properly.

The heater gasket is out.

removed the 2 bolts and pulled the fuel filter housing up while the engine was running... no evidence of leaks from the housing its self or the 3 hoses that are visible.
appears the leak is coming from towards the front of the engine, the valley under the intake is filling up with fuel and dripping out at the rear of the block.

leak got worse today, engine started running rough and I got a check engine light (code 251 and 370 stored)
Guess I will pull the intake manifold and find out whats going on. hopefully its just the return hose from the IP to the filter housing thats leaking, or one of the injectors lines.

check the lines going to and from your IP

Your hoses may be bad.

There are 2 of them, one to the IP as mentioned by Axiom and one goes to the t-valve.

yep... replaced the rubber hose from the drain on the filter housing to the T valve. also found the o-ring on the bottom of the water seperator was hard and brittle.
this appears to have fixed the leak.

good thing I did all this too... fuel filter was nasty and the housing was full of rusty water !