On xkcd, Randall Munroe posted a list of "words for small sets", saying that all of the terms "several", "a few", "a handful" and "a couple" basically mean "2 to 5". For me, however, I've always felt more like this:
A few: 3 to 5
A handful: 4 to 6
Several: 7 to 10
A couple: 2 or 3
It would be interesting to conduct a very large survey of internet users, presenting them with a small collection of objects (anything from 2 up to about 12) and asking them to choose the most appropriate descriptive phrase out of those four, or "none of the above". You'd probably need quite a lot of data to make any conclusions, and you'd want some other participant info such as gender, age and nationality to dissect the results further. I think that would be an interesting experiment, along the lines of xkcd's own colour survey.
Then again, you'd probably end up with exactly what he posted in the first place.
Mokalus of Borg
PS - Personally, when I say "a handful", I'm usually speaking literally.
PPS - That is, "put as many in your hand as you can hold".