I don't think there are any PDIP or SOIC chips with functions similar to the FTDI chip (USB to serial.)
One possibility is to use a micro (like another AVR) with either included or "fake" USB capability.
For example, see http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1248737449
I believe that the fake USB code for AVR will run in some of the 8-pin "tiny" parts, and I think it's freescale that has some 20-pin (DIP, SOIC) parts with HW USB (MC68HC908JB ?) (Hmm. And Microchip, these days. PIC18F14K50)