This tool allows you to easily clean the LaTeX code of your paper to submit to arXiv. For example, it removes comments and optimizes images.
Detexify helps in writing complex LaTeX symbols, similar to Shapecatcher for Unicode. It searches for the correct LaTeX macros based on a drawing of the shape the users wants. It is a better way to search for symbols instead of going through the symbols-a4.pdf manually.
The IETF now provides official bibtexs to download. They work for RFCs, BCPs, and drafts.
The bibtex for BCPs work, but only, if the BCP consist of a single RFC. If the BCP consists of multiple RFCs, the bibtex will only show the first one.
For drafts, the draft version number, the last two digits, have to be removed from the URL.
Search through the documentation of TeX and LaTeX packages. It provides each access to the package documentation, examples or readme.