Should You Ask a Geologist?
To get questions answered on the Internet, the old ways may be the best.
Ask an Astrobiologist
The NASA Astrobiology Institute runs this space-related site. You must register to be able to ask a question, and your answer will take a few weeks, but there's a lot of benefit besides the question service if you join up.
The University of Hawaii says they take a couple of weeks, so see if your answer is already here in the FAQs.
Ask a Geologist (U.S. Geological Survey)
Since late 1994, this government agency has taken questions from the public. Some 150 different scientists participate.
Ask-about-Geology (British Geological Survey)
Those in the UK are especially encouraged to submit questions to Central Enquiries here.
Mike Strickler, an instructor at Rogue Community College in Oregon, has answered 87 choice questions so far. Worth a browse, and check out the rest of his Geomania site.
Hosted by the Microscopy Society of America. Click on the Reference & Educational button to find it. Submit questions via the form (usually takes about a week), or see if someone is available live to ask via telepresence.
Ask Mikey the Geologist
Part of the great Rockhounding Arkansas site is this page where Mike Howard takes and answers questions. Don't ask him where the great collecting places are in Arkansas, though—he already has a fine rant about that.
The Internet Public Library
They don't promise an answer in less than three days, but like a real librarian they'll give you lots of places to find your own answers. This page is where you submit questions.
"The laboratory that never sleeps" accepts your questions and tries to answer them within two weeks—assuming your answer isn't already on the site. Hosted by Washington University Medical School.