Mindat.comWhile mindat.com is a great resource to search, please note that if you register to participate in the forums or contribute to the galleries, the member user agreement allows all your public contributions, comments, and posts to be kept visible on the website permanently. Should you want any of your content removed at any point or your account deleted for privacy reasons, you will find it difficult if not impossible to get the moderators to comply with your request.
Earth: An Introduction to Physical Geology by Tarbuck & Lutgens (any edition). This is a very accessible textbook with many images; it is an excellent starting point for learning geology fundamentals.
Facebook groups: there are many general groups (just search "paleontology" or "fossils") as well as specialized paleontology groups for different geologic time periods or types of fossils. Be aware that many groups have a mix of both professional paleontologists, experienced amateur fossil hunters, and hobbyists. Be very discerning about the advice you take.
Fossil hunting & paleontology posts Check back for upcoming posts on the following topics:
How to find places to fossil hunt
What should you keep in your backpack?
Cleaning and preparing your fossil finds
Is paleontology the same thing a geology? What about archaeology?
Cataloging, storing, and displaying your collection
What is pareidolia?
I think I've found a fossil. Where can I get it identified?