Several people have been discussing USB here of late.
Zilog have announced a new processor (Z86U18) with inbuilt
USB support. A PIC it's not but hopefully Microchip are in
hot pursuit and will have something equivalent in due
course.

Specs include 1.5Mb USB "engine" @ 6MHz (1/4 clock rate), 32
i/o in a 40 pin dip pkg. Also in PLCCV QFP & SOIC.

Also announced is a Z8E520 apparently targeted at USB mouse
type applications.