I would like to know which numbers I could expect for a new
interesting freeware program released on the internet without an
investment in advertising. Suppose I have a program for a broad
audience of not technical people, just regular internet users; I want
to give it away for free, so I just submit my website to search
engines and shareware collections; then I just wait and see how many
people download it.

The following would represent a sufficient answer: some historical
data (not too old) about any free (or shareware) program that became
widespread (at least 50.000 users in 6 months) without a significant
investment in marketing, with the monthly growth of user number for
the first year.
I already have the data for Incredimail, so that wouldn't count.