This site, along with a few others, originally ran off of a Raspberry Pi Model B (rev. 2). Two thumb drives with a few scripts managed backups and my fibre connection meant speed was reasonable for my purposes. I've since migrated everything over to a droplet on DigitalOcean so that I could free up my Raspberry Pi for other projects.
Running on this same little server was:
Running on PHP+Apache. I use a push-to-deploy mechanism. A couple of password protected directories function for FTP’s. The Pi pinged my DNS service regularly and my domain provider pointed to their name servers, meaning that it was plug and play - if my internet went down I could just plug it into a neighbour’s or friend’s and be up and running again 5 minutes later.
GitHub is great for public projects but the price tag on private repos is a bit high for my limited needs. So I used Gitolite and a git user for user management for all my repos. The SSH key authentication of Gitolite is perfect. I don't really use GitWeb myself, but for any collaborators, commits and diffs can be browsed that way too.
There’s also a mediawiki available specifically for Codename: Eureka, containing all of the dev and style guidelines as well as story, images, planning etc. A basic vanilla install with limited customization, but handy for documentation.
Using Mantis, I have a bug tracker for Codename: Eureka too, though this is admittedly overkill for the size of the project. Advantage is that it hooks up nicely to the git server letting me close issues, append commits etc. all through tags in the commit message. e.g.
git commit -m "changes this code, fixes #123” will append the commit ref with that message and close issue #123. Automation FTW.