Intel and AMD are the biggest companies, though Intel is probably the most popular.  The current lineup of Core processors includes the latest Intel Core i7, <a href="www.intel.com/en_uk/Consumer/Products/Processors/corei5.htm">Intel Core i5</a> and Intel Core i3, and the older Intel Core 2 Solo, Intel Core 2 Duo, Intel Core 2 Quad and Intel Core 2 Extreme lines.