Resources
Department of State
A great place to start looking for things about visas is the US Department of State's travel page. The page includes links to information on passports, and visa applications.
The Visa Bulletin is particularly handy for folks who want to know whether their priority dates are current.
USCIS Links
The USCIS site is deep and confusing. In addition to the main USCIS page, there is a ton of information. Petition based applicants are often directed to the case processing time page.
American Immigration Lawyers Association
AILA has a lot of resources for both clients and their attorneys. Try their tool to find a lawyer.