People ready to respond to questions.
To get questions answered on the Internet, the old ways may be the best.
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.
That's the title of the page, but this service of the University of Hawaii has the URL "askanerd.html." They say they take a couple of weeks, so see if your answer is already here in the FAQs.
Since late 1994, this government agency has taken questions from the public. Some 150 different scientists participate.
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.
This page at the University of Hawaii also takes your queries about marine instrumentation.
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.
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, thoughhe already has a fine rant about that.
The University of Hawaii has a special page for mineral and ore-related questions.
Write to the experts at the University of Hawaii, where volcanoes abound.
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 weeksassuming your answer isn't already on the site. Hosted by Washington University Medical School.
NASA's Mars Quest specialists will take your questions. Just make sure to read the page first.
The U.S. Geological Survey's Terraweb site takes questions from kids about how satellites are used to learn about Earth.
The Oregon Museum of Science and Industry takes and answers questions. This page is the Geology section, just one of many. They say they take 2 to 6 weeks to answer you, if they answer.