The session timeout is a function of the app server. To adjust this check your installations web.xml. This link should provide some more info for you :
Let me know if you have any trouble applying this.
Is there any way to adjust the amount of time someone can be logged in on Clearspace, seemingly inactive, before getting "timed out"? I imagine this is a system property?
Nate is right about this being a function of the application server, but one thing you can have your users do right away is to have them click the 'remember me' checkbox when logging in. If they do that, they'll be logged in for 30 days (although this can be changed by modifying the jive property 'AuthFactory.autoLoginMaxAge').
Also, is there an "autosave" option, that would automatically save a document draft every xx minutes?
Yes, there is an autosave function and it actually fires every 30 seconds in the background on documents, discussion messages and blog posts. We designed it to be more of a 'recovered document' type feature that will alert you if your browser crashes before you have a chance to save a document for a variety of reasons.