I've been searching the net for a tutorial on implementing one of the victory lifts (lift_platform.mdl), but I can't find one. The valve tutorial for a "simple two-stop elevator" is for one with some complicated doors. Is there a simplified version for newbs like me? And is there anything special that needs to be implemented in Portal for it to work properly?

I'm not sure if this is the best way, but I would make a func_door with nodraw as a texture, add the prop_dynamic with appropriate model and any other accessories parented to the func_door

then, a trigger_multiple brush with trigger texture applied to it, sitting on top of the lift with the appropriate outputs

onstarttouch -> func_door -> open
onendtouch -> func_door -> close

the trick is choosing the right speed, and finding the right value for the Lip parameter in the func_door. Also make sure the other parameters are correct, make sure its set to not automatically shut unless thats what you want. check your flags, etc.

That did the trick. I might post it on here later as a prefab or quick step-by-step guide for reference.

Unfortunately, there doesn't appear to be a model for the cylinders the lifts ride on so I can't make one a prop_dynamic. Should I just make one a func_detail?

no you'll need to make it a func_brush and then parent it to the func_door
func_detail can't be parented

Hrm ... I just noticed I get a recurring:
Interpenetrating entities! (player and func_door)error in red in the console whenever I use the elevator. Any way to disable this message or am I doing something wrong?

and you have nodraw applied to the door, and a prop_dynamic parented to it right?

try putting a player clip over the top of the elevator, so you're actually standing on that, remember to make it a func_brush and parent it to the door as well