The main close call I had on this project was that there was only one package that supports generating excel spreadsheets, and it's a labor of love by one person. This wasn't a huge issue for me, I had a plan to write csv and then convert if it didn't work, as I didn't need formatting/fancy output. It turned out to work great, so that wasn't necessary.

There was an excellent transactional email library that hooked into the standard templating system, and a few so-so approaches to authentication. I ended up rolling my own on top of a decent crypto library.

For the non-web-speicfic bits I haven't found this to be an issue, Erlang has a whole kitchen sink with OTP (even if like a real kitchen sink it's a bit grungy if you look inside), and I've found plenty of algorithm/data structure-y packages.