Mikkel,

Michael gave you his opinion of a chip he has used and likes. There are tools available for that chip and maybe the price is slightly high, but as he says, the debug time is reduced because of the JTAG port. Debugging through a serial port works, but what if you are using it in the application?
Analog Devices makes the ADuC834, 62K program
3K XRAM, 512 RAM, 4K EEPROM. This chip is programmed in circuit via the serial port. The software to program it is free from the Analog Devices web site.