I would use tabs in the sidebar for browse by date/tags.
(Like smashingmagazine has for jobs, news, forum)

Social media buttons; use an allinone like AddThis.

Keep all the categories, just clean it up by being in a tab.

Text could be 1 pt. larger.

Other...
remove the calendar
maybe just 10 posts on front page?
add a post voting option, and a way to view popular of day,week,month,all time?