Using photos as a reference point for your design in Illustrator can make the process easier but that doesn’t mean that all of the tutorials below are easy. Some (like the Scanner Darkly one) will take hours for even those well versed in vector illustration. Most of the tutorials use a combo of Photoshop and Illustrator but the few that only use one program use Illustrator. 

Mosaic Tutorial from Design Spice (uses Illustrator and Photoshop) 

B Movie Poster Art Tutorial from Digital Arts (uses Illustrator and Photoshop) 

Imitating A Scanner Darkly Tutorial from Layers Magazine (Illustrator) 

Gigposter Design: The New Sex Tutorial from GoMediaZine (Illustrator and Photoshop) 

Grid Masking Tutorial from Veerle (Illustrator and Photoshop)  

Lichtenstein Style Pop Art Tutorial from Vector Tuts (Illustrator) 

Spoof Airplane Safety Illustration Tutorial from Spoon Graphics (Illustrator and Photoshop) 

Draw Your Self Portrait Tutorial from AiBurn (Illustrator) 

Drawing Figures from Photos Tutorial from Computer Arts (Illustrator) 

Create a Sketchy Hand-Drawn Camera Illustration from Vector Tuts (Illustrator and Photoshop)