You can find plenty of resources in the following books, articles or weblinks.

• CTAN
• The LaTeX wikibook
• Crash Course in LaTeX
• The Comprehensive LaTeX Symbol List
• LaTeX Templates
• LaTeX equations on the web
• LaTeX on MacOSX
• Free beamer themes
• Share LaTeX equations on the web - MathJax
• My beamer themes
• The TeX catalog online (see especially the Physics section)
• Several packages related to greek by Apostolos Syropoulos
• truben.no helps you make tables and bibtex entries
• DOI Citation formatter