Philips IC's can be programmed directly via the UART. for atmel you need the SPI etc. some Atmel chips are UART programmable as well (e.g RD2) and then you have SILabs which program via JTAG and who knows what other means there may be from the various manufacturers. Some of the very small LPC chips use ICP which again require external hardware (not on the board as the Atmel "ISP" mentioned below, but in the cable).

For ISP always fully read up on the chip before you select it. Once Atmel announced an ISP chip and a closer inspection revealed that it was ISP only if you put one more uC onh the board for the sole purpose of programming the other.

Erik