Google changes algorithm Daily. Matt cutts says about it here http://www.youtube.com/watch?v=1_jm_isupFY
ya google changing his Algo and launch New Algo after few days bcz already this time google update is running
dont know about the algorithm change but Google Webmaster is getting some changes, like some Analytics features
What I've noticed for now is that the ranking fluctuates drastically every time I check my website. Don't know if some changes is happening here.
Google run a complex algorithm based on different factors including quality links, optimization quality, bounce rate, referring traffic etc to rate you between one and ten. Though its algorithm is extremely sophisticated, it can be summed up in something like this: Search Ranking = Relevance * PageRank PR is important, but relevance is more important.