My Friday night gaming group uses Slack as our groupware/clubhouse/lobby, Roll20 for our tabletop and dice roller, and Skype for audio chat. That is working pretty well. Oh, and we use Google Sheets for character sheets.
Slack is just okay as freeware groupware. The native dice roller, Dicebot, is pretty terrible. It is a rickety stack of APIs that crashes at least once per session. Which is why we tend to use Roll20 even if we're not on a map.
Roll20 is a bit clunky, probably because it is running in a browser. It is kind of laggy, performance can be downright poor, but it does work pretty much every time for what we use it for. I don't think I would pay money for it, but for the price, it is worth it. We do not use more than a fraction of the features, though. The dice roller is solid, and it is easy to set up macros for things like initiative rolls. We do not have integrated character sheets, so we are just typing "/roll 2d100<68 Observation" for our dice rolls.
Skype has gone a bit downhill since Microsoft bought it, but like Roll20, it does the job and the price is right.
Google Sheets work pretty damn well for our character sheets, we are quite happy with them.
What we used previously:
We started out gaming in a private IRC channel, using Yahoo Groups for our groupware solution, and Excel spreadsheets for character sheets. IRC has decent dice rollers, but no tabletop. We would post maps to the Yahoo Group instead. The Yahoo Group gave us a reliable email list, as well as places to post files for character sheets, character art, and maps. The Excel spreadsheets worked, but we soon switched over to Google Sheets because they were online and worked just as well for the simple things we were doing with them.
Most of us were happy on IRC, but some people just couldn't deal with all the typing, and wanted voice chat. There was also the potential issue of our IRC server going away at some point, since we didn't run our own server.
Yahoo Groups worked well for a long time, until Yahoo abandoned them, and eventually shut them down.