Here's another simple but effective fly. It's called the "E Z Nymph", and it's one of the first I tied. Very easy to tie, and it catches fish, too!
Also from FAOL, take a look at the "Too Simple" nymphs. http://www.flyanglersonline.com/alcampbell/ac011204.html and http://www.flyanglersonline.com/alcampbell/ac040504.html
I've found you can simplify them even more by leaving out the legs, and you certainly don't need to use only "Punch" embroidery yarn. If you can find some "heather" or "tweed" wool yarn that has some highlights of a second color in the yarn you can make some very nice looking nymphs. The best I've found is mostly a charcoal color, but with some brown and maroon highlights (leftover from one of my sister's sweater projects, so I don't know the brand or specific color - but it's deadly!). If all you can find is a solid color, that'll work too. http://www.flyfishohio.com/Frank_Sawyer's_Killer_Bug.htm Use tying thread for an unweighted nymph or thin copper wire instead of thread for a weighted nymph. Basically just wrap the yarn around a 1xl nymph hook with extra wraps to make a thicker thorax area. Rough it up with some velcro and you're done. Doesn't get much easier.