Are there any movies similar to Madman?

You might want to try Humongous. Very similar film and released in the same year.

http://www.imdb.com/title/tt0082537/

Pretty sure it is out on Bluray now.

Others to check out are

Just Before Dawn
The Forest
Rituals
Midnight
Wrong Turn
Hatchet
Don't Go In The Woods

Haha ya, all of the friday the 13ths. Except the first, of course.

Yes Homongous is definitely a movie very similar to Madman and there's also the classic Jason movies. As for Hatchet, its a spoof on slasher movies. The kill scenes are so fake looking and the whole movie is overall cheesy and bad, but they do that on purpose.

Obvious one would be Sleepaway Camp, Maniac Cop maybe? Haven't seen this so just an educated guess or two.

Creepy deformed killer lurking in the woods killing people? Nope, this movie is the only one.

As others have said, Humongous.

I watched Humongous on Monday night followed by Madman on Tuesday night, very similar antagonists.

Humongous was better.