The Macro Data Guide Looking for a dataset? Chances are you'll find it here.
European Social Survey A cross-national survey project. Round 6 contains the very useful module "Europeans’ Understandings and Evaluations of Democracy"
VoxIt A cumulative file of basically all post-referendum surveys in Switzerland. If you're into referendums and/or Switzerland.
ggplot2. The best graphics package out there. Period.
magrittr Instead of nesting functions why not pipe them? E.g. x %>% as.numeric %>% mean %>% round(., 2)
blind, colorblind and plottig. The default scheme looks awful, s1mono has a classic but bland look. Daniel Bischof's themes seem like a promising alternative fixing minor things like vertically aligned y-axis labels.
graphexportpdf As graph export does not produce PDFs under Linux this package is a great alternative to produce PDFs from Stata on Linux operating systems.
todonotes Allows inclusion of comments in the margins and in-line. Great for leaving comments to your co-author.
changes OK, it's not as convenient as track changes in Word but it comes pretty close. Great for co-authoring.
tex4ht Compiles TeX to HTML and ODT. An essential tool if the journal you are submitting to requires *.doc.
and of course
PhD Comics for procastination