Here are the answers to the specific questions with respect to the Q&A websites...there are many other builds in play at Stack Exchange, so limiting this answer to what I think you're interested in:
What software/tooling is used?
We are using TeamCity for our builds, the builds themselves are a combination of MSBuild, PowerShell and custom apps (DB Migrations and what was the CDN purger). For other systems like puppet, they're bash scripts on the linux build agents.
What time are releases generally performed?
Whenever someone says "hey, wanna build?". No, really...we deploy throughout the day with no one noticing usually, other than the build number in the footer incrementing. Maybe we deploy riskier changes in the morning before peak traffic...or that could just be Marc on UTC time having the craziest changes, your call.
How many and what steps are involved?
We may not deploy in a given day (typically only weekends) or we may deploy 20 times a day. I'd say the typical deployments per weekday is somewhere in the 3-8 neighborhood. As for steps it's:
- Check-in code
- Dev builds (continuous integration build)
- Sanity check it works in dev, maybe - we're follow a cowboy deployment model with small changes.
- Build "meta", which is really web servers 10 and 11, but for most purposes it's
- Build "prod" which is really ny-web01 to 09, these host everything except meta, and internal requests (private API) to meta
- If it didn't go well, start drink heavily
This is of course a high level overview...if you have more specific followups I can answer those, or if there's enough interest I'll take some time and blog it. Blogging may be delayed a bit, Pete and I a bit busy with another small project at the moment.
EDIT: Blog about Stack Overflow deployment is here