Google is testing a new collapsible side bar where the search options and filters are after you conduct a Google search.
I reported a couple days ago on Search Engine Land via websonic.nl but now more and more people are seeing this experiment.
Here is an animated GIF to see it in action:

Here is also a video:
The Tecno-Net blog has information on how to replicate this but it means you need to install some things and run some commands. Either way, it seems Google is testing this more and more.
Forum discussion at Google Blogoscoped Forums.

Comments:
thefke
04/03/2012 02:03 pm
new space for AdWords ? :)
3d Designs
04/04/2012 11:32 am
I don't see that option on my computer...
Eren
04/04/2012 11:37 am
Not a huge change to influence the user experience - but the extra space could be used for other reasons. Adwords possibly, maybe more space to promote other Google products.. Is this being rolled out in the US first then the UK does anyone know?
toll free numbers
04/04/2012 11:39 am
I think US would be the first
Henry Huang
04/10/2012 06:30 pm
The dropdown shouldn't collapse after you choose search type. It looks like after you click image, the dropdown collapses again. It should stay open.