Most of those look like important system services (logging, cron), that you might be able to mess with if you're feeling brave, but I wouldn't recommend it. SSH is optional, but I'm guessing that's how you're connecting to your plug, so can't get rid of that.
The only exception is "ondemand"; I'm not sure what that is (and it doesn't appear in the Debian install I have on mine). Okay, a quick search tells me it does CPU frequency scaling, which you maybe don't want if you're going for the best performance. But you should find out more about it first.
If you want to learn more about any of the services being started, you just need to find out what package they belong to. Just use "dpkg -S" on the script in the init folder and it will tell you (eg. "dpkg -S /etc/init.d/ondemand"). Then use "aptitude show" to get more information about that package (eg. "aptitude show initscripts").
Oh yeah, and if you're going for the fastest possible boot, there's only so much you can do by fiddling with system services. If you want to get faster, you're going to need some deep magic that is well beyond me.