A thought about the "latest" potion of the sidebar: I'd personally prefer it showing one-two from each category rather than a handful across the boards. So two latest in free, two latest in casual, two latest in advanced - otherwise the slower-posted forums won't be getting much limelight. 

(I'd also suggest melding NRP section back into Free/Advanced/Casual and making NRP a tag, but I doubt it is going to happen... Perhaps once we have tag-based filtering/search? Since in all honesty, I've been basically out of the NRP scene ever since it became its own thing, solely [i]because[/i] it became its own thing and was no longer by tier.) 

I myself am partial to right-align for the sidebar - for a forum such as this, I'd prefer the actual forum-portion to be in the main focus when I visit the page (and left-aligned things tend to be the main focus for humans, at least those using our read-from-left-to-right text, as some research found out), and the sidebar be something I look at secondly when I am not doing something specific. Left-aligned sidebar would be a bit too obtrusive for me for a forum (if we were a Wiki, where'd you'd foremost access things by category/article, then things'd be different; in forum, the subforums are the main "categories" I'm interested in, not the individual RPs). 

In regards to Open/Closed tags:
I find Ellri's suggestion is a bit too much division. It'd become clutter. 
I'd say stick with:
Closed | Jump in | Applications
(Since "jump in" and "apply" already suggest that the RP is open. ..."Apply (CS)"? "Apply (NS)"? "Apply (sheet)"? Ehh, I assume people probably don't want applicants who don't bother to skim the OP after they see the RP is taking applications...)

Edit: 
Horizontal lines are useful for posting multiple characters at once.