My wife and I either buy off their registry or give one of these:
http://www.brooksbabygifts.com/category/Baby-Diaper-Wreaths/c45
We got them for both of our kids, and as hard as it may be to believe they are very cool to receive. They can have more than just diapers on them too.
Also, in my experience all the guys invited end up bailing out and sending a gift unless it's a shower held at the workplace.