I am writing the comments above so that this question does not remain unanswered. As Qiaochu Yuan writes, one good resource is the wikipedia page for etale homotopy theory. Here are two references from MathSciNet.

MR0883959 (88a:14024)
Artin, M.; Mazur, B.
Etale homotopy.
Lecture Notes in Mathematics, 100. Springer-Verlag, Berlin, 1986. iv+169 pp.
ISBN: 3-540-04619-4

MR0676809 (84h:55012)
Friedlander, Eric M.
Étale homotopy of simplicial schemes.
Annals of Mathematics Studies, 104. Princeton University Press, Princeton, N.J.;
University of Tokyo Press, Tokyo, 1982. vii+190 pp.
ISBN: 0-691-08288-X; 0-691-08317-7

Here is the URL for the article of Michael McQuillan: Elementary Topology of Champs.