Many derivatives have integrated flash memory. Some of those derivatives allow you to partition the flash memory between data and code memory, all on-chip. Texas Instruments MSC1210 comes to mind.

Keep in mind that flash memory has a limited life in terms of the number of writes a given cell can handle. So don't use flash as data memory if you'll be updating that memory 100 times a second or something like that--you'll exceed the write endurance of the flash memory real quick.

Regards,
Craig Steiner