KY had passed this to me quite a while back but I had forgotten to share this to everyone till now. Click on the picture to assess the website where the PDF can be downloaded. (The link to the PDF seems to be broken when I am typing this entry. Hopefully it will be restored soon.)
The State of Observed Species (SOS) gave a short report on our current (correct as of year 2008) number of described species in the world.
And here is a summary of the various taxa at a glance.