about the alignment of the members online block
leave it as it is...why??
because in your first category you only have 2 forums and most it would be aligned jusat for 2 forums, and if anyone would add more forums it will not be align so leave it
also try to user a diferent color for the thead of side bars to be diferent from main theads and will give nicer look overall
also try another font for the user bar buttons ( maybe roboto or Jaldi)
overall it looks good and clean
keep up
cheers
SubzR