love kolo — so lovely, who doesn’t! — and here are a couple of other options from etsy folks that might be customized for personalized guestbooks as well –

eklecktic makes modern photo albums/guestbooks –
http://etsywedding.blogspot.com/2007/06/ecklectic-wedding-album.html

also seelou makes lovely books that one could customize for a journal:
http://etsywedding.blogspot.com/2007/06/seelou-storymade-customized-journals.html

and there’s always littleputbooks.etsy.com — all great!