How do pesticides "attach"
>themselves to the produce?  Are they only on the surface of the fruit or
>vegetable (and therefore can be washed or peeled off) or do they
>permeate the entire organism (in essence, the fruit or vegetable acts as
>a sponge and "soaks up" the pesticide, making the entire produce
>contaminated)?

The pesticides residues on crop can be detected by analyse .my guess will be
that they are absorbed by the tissues. You can feed plants with fertilisers
thru foliage spraying, so it seems logical that any contaminants soluble in
water could be absorbed that way. Now the pesticides residues is just a
small part of the problem of non organic agriculture. The main one being
that liquid fertilisers are absorbed indiscriminatively by the plants
creating imbalance in nutrients, causing the plants to be diseased  and weak
and more subject to predation .
The mineral content of crops organically grown in general is more than in
non organic ones.
So you end up with a tasteless produce ( taste is very much in correlation
with mineral content) ..
On top of that the consequences of chemical agriculture is far feyond the
problems of pesticides residues. the Bigg one is that fertility of soil is
decreasing over the years making the land more and more dependant on outside
fertilisers to maintain production . That lead us toward a global
desertification process that is most spectaculary seen on the edge of
existing desert but that is true everywhere where farming is occuring.
buy organic as much as you can and you will do good to yourself and the
future generations.
at this site you can see which foods are the most contaminated by pesticides
http://www.foodnews.org/index.html

for an extensive list of links related to organic farming see
http://www.rain.org/~sals/my.html

jean-claude