Jason Shiga's 2001 comic "Fleep" is about a boy who wakes up in a telephone booth that has been mysteriously encased in concrete. With only the content of his pockets (two pens, a paperback novel, three coins and 20 feet of unwaxed dental floss), our hero has to fashion an escape plan before he runs out of oxygen ....
Fleep is a geeky fun comic, featuring an exciting use of math, and with a dark twist at the end. Check it out: http://www.shigabooks.com/strips/fleep/scrollindex.html - Thanks sparge!
Oh and thanks Alex, I spent the better part of an hour last night looking for this comic, post faster next time. ;P
and I got very claustrophobic. :)