Maxim has a lot of converters...but you can try "classic" 75LS176 from Texas Instr.
BB Electronics (**broken link removed**) has some applications for 485 interfacing.
used cable which come with shield wire and used DB9 conectors and conect the shield wire with the metal part of the DB9 conectors or outer
body that it's keep in mind this can be done on both ebd of DB9 conectors
Normally RS 232 is able to work up to 20mt (according to the standard). This limitation is due more to a problem with electric level than to the speed: today every RS232 is able to sample the incoming signal up to 16 times the maximum speed and recover the front.
bye MRM