I found the following from the PIClist archive
and it claims to be better than Andrew Warren's 
LFSR. Why?

Regards,
Xiaofan

;*****************************************
;PRNG 8 bits
;by Nikolai Golovchenko
;Seed RANDOM with a number different to 0
;during initialization.
;This code gives less sequential repetitions
;at edges  (0 to 32, 224 to 255)
;than Andrew Warren's
LFSR:
     CLRC
     RLF     RANDOM, 1
     SWAPF   RANDOM, 0
     ANDLW   0XE0
     RRF     RANDOM, 1
     ADDWF   RANDOM, 0
     ADDWF   RANDOM, 0
     ADDWF   RANDOM, 0
     SUBLW   0X35
     MOVWF   RANDOM
     RETURN
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