The Maxim DS275 Line-Powered RS-232 Transceiver Chip is an ultra low power RS232 interface that only requires +5V and tests out as ideal for the Arduino. It gets its -VE transmit by stealing it from the incoming RX - sneaky little trick 
(just like the two-transistor circuit in the original Arduino Serial, at several times the cost?)
... probably with the same reliability issues as the transistor trick.
-j
I can't actually see the point in this chip. First of all it is only designed as a half duplex device. That means you can't transmit and receive at the same time. Second if you need to supply +5V then you might as well have a 'real' chip like the max202 that generates the negative supply, that only needs +5V as well.
The main problem about passively powered RS232 devices is that you are stuffed if there is on on each end of your link. 
The main problem about passively powered RS232 devices is that you are stuffed if there is on on each end of your link. Wink
Good point - that one never occurred to me :-[