This On-line Cross-Reference can be used as a resource to match up an Atmel part with the part you are currently using from another vendor. After a quick search, you will have the information needed about the equivalent Atmel part at your fingertips.

Select a competitor and then enter the part number that you wish to do a cross-reference on. You must enter the designated number of characters for the competitor part number in order for the cross-reference to pull up the Atmel counterpart.