Opportunity must be driving down Meteorite Alley on Mars. The rover has come across still another meteorite, the third space rock it has found the past few months, and fourth overall since 2005. This one is called Mackinac, which continues the "island" theme by which the science team has dubbed the meteorites. Block Island was found in July 2009, and Opportunity came upon Shelter Island the end of September (around sol 2020 for the rover). Mackinac was found on sol 2034 (Oct 13), and it looks very similar in composition to the two earlier meteorites. Opportunity analyzed the Block Island and found it was made of iron and nickel.
You can keep track of Opportunity's travels through Meridiani Planum on its way to Endeavour Crater at one of Stu's blogs, Road to Endeavour. But — and this is very fun — you can also follow Oppy on Google Mars, and see where it has found the meteorites. Tesheiner on UMSF regularly updates a route map, pinpointing the spots where the rover stops. Just go to Google Mars (download Google Earth and Mars here if you don't have it yet), open up Google Mars, then click on this link, download and open, and you'll be transported to Opportunity's location on Mars. Extreme, extreme cool.
Thanks to Nancy Atkinson from Universe Today