When jets fly over my house sometimes they have contrails coming off there engines...well do prop aircraft have contrails...like the Dash and such commercial props?

Contrails are in general a subject to exhaust temperature and the the SAT.  Depending on winds and SAT they will be visible for a longer time.

Props tends to fly at lower altitudes where the temp. is much warmer so there is one reason you don't see contrails after props...

But if a Dash-8 would fly at FL370 it would most likely produce contrails awell.

Well, I haven't seen many B-17's on photo regardless.  
But that webpage seems to confuse contrails and vapor trails/wing-tip vortices, or am I experiencing a language barrier here  ???

There seems to be some confusion over the definition of the word "contrail". I'm not sure when it was first used but I think it's comparatively recent. Trails in the sky caused by an aircraft were commonly called vapour trails during WWII (& when I was growing up in the 1950s). These famous photos show the "vapour trails" after combat over St. Paul's cathedral in London during the Battle of Britain. This was a common sight all over south-east England in the summer of 1940. They would be called contrails nowadays.



PS. Like the B-17 photos these trails were left by conventional piston-engined aircraft. It's worth remembering that the Dash 8 is powered by turboprops which are basically gas turbines (jet engines) driving propellers.