There is no single guidebook for South America. That would be one helluva' project. There is a paper book for Ecuador [ see Small World Adventures website ] maybe an online guide as well. Check out Peru Whitewater,this guy Kurt Casey has put together an online guidebook that is pretty sweet. He has one for Chile including several runs/rivers in nearby parts of Argentina.I seem to recall there was a paper Chile book as well. I think Damon Miller had or was working on a Peru book or website but don't know any details. I would guess there must be some sort of book or site for Brasil,probably in Portugues [sp ?]
Colombia is rich in whitewater but security issues have kept exploration relatively low.
Venezuela has runs in the Andes around Merida and big water rivers around the Gran Sabana and Guiana Highlands.
Bolivia has some potential. Someone on this forum posted about some 1st ds not long ago. You can take the Yungas death road over to Coroico where there are some runs and i think an outfitter[?].There are multi day trips on the Beni and Tampobata,the latter might be Peru. Seems like not a lot of exploration yet in southern Bolivia.
Uruguay and Paraguay, not mountainous so probably not much.There is paddling around Iguacu Falls,not sure if it is whitewater or on the Paraguay side
The Guyanas would be hard core exploration,very underdeveloped !!!! I have a map with tons of marked rapids,that could be 2's or raging high volume monsters like Kaiteur, 23,000 cfs avg . on a nearly 800 foot falls with class VI [?] rapid at it's base. There are several other falls that rival Kaiteur ,believe it or not. I have only ever seen one ad for a commercial trip in Suriname and some French guys running 3 ish stuff in Fr. Guiana on you tube.
Some people refer to Central America as ' South America.Check out www.MAYANWHITEWATER
for Chiapas, Guatemala,Belize,El Salvador,and Honduras.Be sure to click on 'other' then Panaraimo for an awesome collection of river photos. There are two guidebooks for Costa Rica,'Chasing Jaguars 'and an older one.'Honduras the Undiscovered Country' is hard to find.Check Boquete Outdoor Adventures for Panama.Lonely Planet had some general beta about rivers near Boquete in an older edition. Nicaragua = next to no beta, the Canoandes group 1st 'ded Rio Matagalpa years ago,google Matagalpa kayaking images,looks like big water 4 with crocs. Upr. Cocos has some 3.
Can't not plug SierraRios for Mexico after all that.Rocky is the MAN,Greg too.