Cool urban vector art mega pack in Adobe Illustrator, free to download. Vector art set includes some amazing cityscape illustrations, people silhouettes, graphic clip art and grunge effects. Graphic designers, visual artists and illustrators can always use some cool vector art footage.
an image from the US government EPA "Sunwise" program. I converted it from PDF format, and removed all the "sunwise" logos. the source link is here - http://www.epa.gov/sunwise/doc/mission_story.pdf