Originally Posted by
cyccommute
I have a Performance Transit Epic that has lasted for more then 5 years. Not terribly waterproof but if that's an issue there's always ziplocks

It expands (rarely used feature), has 3 side pockets and one top pocket as well as elastic straps on top. And it was...and is cheap.
+1, Performance blows these out in their retail stores at the end of every summer...