How do I reclaim the "other" space on my iPad? I have 3.3 gigs of space in the "other" category on my 16 gig iPad. The space for "other" has grown over time. 
I've synced. I've powered down. I've turned all running apps off. 
How do I reclaim this used space that I'm not using?
The "Other" space is not necessarily unused as you imply.  It could simply be your user data from your applications.

If you check in Settings &gt; General &gt; Usage you can gauge how much space your apps are using up including their data (might be photos, or podcasts, or pictures, or anything).

For example, my Instacast it taking up 406Mb of space, but the application is only 3.3Mb.  So that's over 400Mb of "other" space taken up right there:

 

If you were to add up your the data in this list, then subtract the total amount of "application" usage from it, it should pretty much equate to the bulk of this "other" data.  Of course, there are other things that are included as "Other", including your mail data, sms messages, internal log files and location data stores etc etc etc which may fluctuate over time but the big portion is just your apps contents.