PS I am new to this forum etc. - and posted this on the old thread but then thought that people might not see it there. If I should delete this new thread to avoid duplication - please let me know and I'll be happy to do so!
In 1.8 and 1.9 this is a standard feature. When you go to configuration - global settings and then products, there should be a show cart after adding item or something like that (using dutch translation of Nop, so not sure what the exact name is). But when you uncheck it, adding an item just give you a popup message and not the cart.