If you're REALLY curious, handy and have loads of free time, here are a few ideas :
For the Mrs. ("We're gonna need some CAULK" - That part cracked me up)
Homemade "Fleshlight"
And here are two sites aswell :
Best Homemade Sex Toy | Homemade Male Sex Toys for Guys SexToyScientist - Open Source DIY/Homemade Sex Toys (this one looks a bit complicated though)
Although I look very well documented on the subject, 2 minutes of Youtube and Google sufficed. I've never tried any of these so I can't really give you my 2 cents on the matter, I just think it looks rediculously funny
Have fun !