Hi Sally & Pauline.
Actually, both "Buñol" (not Bunol, the Lonely Planet needs to find a keyboard with an "ñ" on it

) and "Bunyol" are correct as they are the name of the town in 2 of Spain's 5 official languages.
"Bunyol" is "Valencian" while "Buñol" is "Spanish".
Just as you will see the word "Cataluña" in "Spanish" with the spelling "Catalunya" in "Catalán". Chalk it up to a lingüistic thing but when in Rome... "Bunyol"

The official (or as close as it gets) website on the event is at
www.tomatina.org ( points to
www.lahoya.net/tomatina ). Even have a webcam
HERE 
As far as I know there are no guided excursions to the festival, it is more of a do-it-yourself trip but is you are interested in going as a group, you should try to contact the folks at
www.forocio.com as they (based in Madrid), offer customized trips and excursions.
Saludos,
jer...
p.d. If you are a lady and are planning on going to La Tomatina, wear a sports bra or tight sports top top since your t-shirt WILL be torn off during the tomato fight!!!
madrid nut, webweaver of
www.multimadrid.com and keeper of the
plaza-cam &
sol-cam-------------------------------
rent a cell phone from me for your stay in spain, more info at
www.onspanishtime.com :-)