RometoRio shows a route for both bus and train.  Several, in fact.  Each varies by price, and time, for obvious reasons, and it's shown alongside some flight prices as well, if that's a possible consideration.

The bus option looks brutal, however, as they're only finding one that goes via Argentina(!), taking 3 days. The train, on the other hand looks more doable for 43 hours, and looks to be split about 1/3 train 2/3 bus.

There is also a flight option shown.

Bolivian buses, from experience, are a far 'rougher' affair than Argentinian/Chilean/Peruvian buses - I wouldn't worry about several days on those, but in Bolivia, it may be a different thing to consider. Personal preference and all that. 

Good luck, let us know what you find!

Traveling into Brazil from Bolivia by land/bus
I've decided to check this site out since it was tweeted by the great Jeff Atwood himself. The first question I saw was "Advice on making ruby code more ruby-like", which is the kind of question I see all the time on Stack Overflow.

So what is the difference between the questions on SO and the questions here? It seems to me there is enough overlap between the two that the difference is not clear, and I may not be alone in feeling this.  So far this site seems redundant.
