bikely.com is a good place to start. you'll have to sift through a lot, but there are plenty of routes that you should find enjoyable. one of our members here has a number of good ones of varying ranges: http://www.bikely.com/listpaths/by/bjanaszek
i highly recommend riding north out of the city. there's just tons of low-traffic, rolling hill, country roads that are all in good condition. and pretty scenic in spots. saxonburg, dorseyville, middle, and all the main drags through fox chapel are fun rides, and you can wind your way out to (or past) the red belt and back if you want to add a bit of distance. it's where i do all my moderate-to-long distance rides.