http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&tpl=/ecfrbrowse/Title26/26cfr31_main_02.tpl (electronic code of federal regs for the internal revenue code)
http://www.leginfo.ca.gov/calaw.html (California code)
http://www.treasury.gov/resource-center/tax-policy/Pages/default.aspx
http://taxprof.typepad.com/taxprof_blog/ (well known tax blog)
http://evans-legal.com/dan/tpfaq.html (responses to frivolous tax defier arguments)
www.irs.gov (can get you a lot of info, but without cites, on substantive and procedural tax)
http://www.justice.gov/tax/readingroom/foia/tax.htm(manuals galore)
http://www.law.cornell.edu/uscode/ (easy to access code, but can be one to two years out of date so be careful)
http://www.adl.org/mwd/suss1.asp (more responses to frivolous tax legal arguments)