Software

Find unicode characters on MacOS: Character Viewer.
Autoreplace LaTeX commands with unicode math in Mac text fields, including mobile: Back up and share text replacements (see also my .plist of text-substitution rules, further Twitter discusison)
Find a unicode character by drawing it: ShapeCatcher.

LaTeX word count: TeXcount.
See LaTeX in your Gmail and GChat: GmailTeX (real-time, browser plug-in required).
Instant Markdown and LaTeXing in browser: Socrates (hyperlink-shareable, no plugin required).
Produce LaTeX images online: Roger's Online Equation Editor.
Find the LaTeX name of a symbol by drawing it: Detexify (available as MacOS menu bar app).
Exports citations directly to BibTex from Google Scholar: Google Scholar Settings.
Converting bare text citations to Bibtex: Reference Tagger.
Converting bare text citations to DOIs: CrossRef's Simple Text Query.
My LaTeX header file (bra-ket notation, etc.): riedelheader.tex.
Elegant templates: LaTeX Templates.
LaTeX equation image creation: LaTeXiT.
LaTeX editor: TeXstudio (with MikTeX).
- Pro: Intelligently runs just latex, or the full latex-bibtex-latex-latex sequence, depending on what's necessary to fully reflect changes made to the source.
- Pro: Search and replace with regular expressions.
- Pro: Sensible placement of error log window.
- Con: Weird bugs, e.g., takes you to the correct line number but wrong file when you double click an error.
- Con: A bit ugly.

Mathematica Autosave!
Fast partial trace of multi-qubit density matrix: [Mathematica Notebook] [Plain ASCII].
Fast, formula-based computation of Gaussian integrals: [Mathematica Notebook] [Plain ASCII].