Let's start with your tax dollars at work. Penn State University operates a Cooperative Extension Service across the Commonwealth.
There are two webpages for PSU's extension programs:
Here's a link to one, for the PSU Extension (link from the Department of Horticulture).
Here's a link to the other one, for the Cooperative Extension (link from the College of Agricultural Sciences).
Penn State has a Cooperative Extension Office in Allegheny County, which is quite active in a number of ways.
Here's a link to the webpage for the Cooperative Extension in Allegheny County.
The Penn State extension trains Master Gardeners, as part of a long-standing national program to train Master Gardeners through publicly-funded state universities and, through their volunteer efforts, deliver knowledge about agriculture to local communities.
Here's a link to the main webpage for the Penn State Master Gardeners program.
The mission of the Master Gardeners program:
The mission of the Penn State MG volunteer program is to support the Penn State Cooperative Extension by utilizing research-based information to educate the public on best practices in consumer horticulture and environmental stewardship.Among the educational programs now in full swing and supported by the Master Gardeners here are efforts to educate the public about the importance of pollinators (love your bees: plant a pollinator-friends garden!) and the "Don't Move Firewood!" campaign to limit the spread of the Emerald ash borer.
Here's a link to the main webpage for the Allegheny County Master Gardeners.
Here's a link to a related website for the Allegheny County Master Gardeners.
The Master Gardeners of Allegheny County engage in a host of community projects -- demonstration gardens in North Park and South Park and courses throughout the county (the "Backyard Gardening Lecture Series") on gardening and, for fruits, herbs, and vegetables, what you can do with the produce. Sandy Feather, who works for the Cooperative Extension in Allegheny County, writes a Q&A column on gardening for the Post-Gazette.
The Penn State Master Gardeners staff a FREE call-in service provided by the Extension for your gardening questions: Monday through Thursday from 9 a.m. to 1 p.m. from March 16 through October 29. Call 412-473-2600.
For more information about the Master Gardener program in Allegheny County contact them at 1-412-473-2540 or firstname.lastname@example.org. The PG ran a nice feature recently on Penn State Master Gardeners, what they do, and how to become one.
Allegheny County also offers extensive information about gardens and gardening. Here's a link to the County's gardens webpage.
Finally, on the not-for-profit but private side, the Phipps Conservatory and its Master Gardeners also offer free gardening and other horticultural advice. (The Phipps Master Gardeners program is not part of the national network of Master Gardener training supplied by state cooperative extension services.) Here's a link to the Phipps info page. That page includes an email form for questions. Alternatively, you can call the "Dr. Phipps GreenLine" anytime at (412) 665-2364.
Last but not least, I looked around briefly for active Pittsburgh gardening blogs and came up mostly empty-handed. I did see the Pittsburgh Gardening Experiment, a forum for urban gardening. What did I miss?