This stuff is fantastic. As far as I'm aware, Agfa Ultra 100 produces the most insanely saturated color images possible. It's not a great film for general use (skintones in particular are pretty unflattering), but there's no better option for creating images with deep, intense color and reasonably balanced saturation.

Here's an example: I used Ultra film in this gallery of snapshots taken with a Lomo Colorsplash camera. I used Agfa processing to develop the negs, and scanned them with an Imacon Flextight Precision II; I did basically no adjustments to the color, other than a little correction on some of the daylight shots.

Rolleiflex 3.5F Model 3 (serial 2266139, manufactured 1964)
Medium format (6x6) twin lens reflex
Taking lens is a Schneider Xenotar 75mm F3.5, viewing lens is a Heidosmat 75mm F2.8

 
Mamiya 7
Medium format (6x7) rangefinder
43mm F4.5 and 80mm F4 lenses by Mamiya

 

Nikon F100
35mm SLR
28-120mm F3.5 and 80mm F1.4 Nikon lenses

Nikon D40
6.1 Megapixel Digital
Nikkor 18-55mm f/3.5-5.6