The Olympus E-P1 and Voigtlander 25mm f/0.95 are a nice combo for bokeh shots...


The Office Christmas Tree 1 by peterb666, on Flickr


Vegemite by Voigtlander by peterb666, on Flickr


Mannequins 01 by peterb666, on Flickr


22 The Artist's Tools - Voigtlander 25mm f0.95 @ f2 by peterb666, on Flickr

The key to any bokeh shot is to get in close to something and to shoot as wide as you can get away with. If you get in really close, you can stop down more than if you subject is a metre or so away. Unless shooting with long and fast lenses, you DO need to get in close.

1) Set your camera in A-Mode and set aperture value as low as possible (fe 3.5 or lower)
2) Focus an object as close a possible (like macro) and keep shutter pressed half way.
3) frame your picture (move camera horizontal left or right) and release shutter button.

This is from a sigma 50mm f2.8 macro. Distance of the subject from the lens also creates bokeh. Here, almost at 1:1, f2.8, focused the lady at the balcony and DOF is razor thin

Details

a little something from me 

Time to Wander by Solo-It-Is., on Flickr

Regarding lens choice, some have said go wide and some have said go long. My understanding is that for equal magnification - i.e. for the same image size of the subject on the sensor - that depth of field is independent of focal length. I.e., put on a 100/3.5 and fill the frame with your subject, look at the DOF, then put on a 28/3.5, walk a lot closer until you fill the frame again, and look at the DOF -- my understanding is it should be roughly the same.

So, for maximum bokeh on a given choice of subject, just pick the lens with the smallest focal ratio (f-number) you have, put it on, and walk to where you need to be to get it the size you want in the frame. Usually that won't be your shortest or widest lens, but something in between. (Traditionally the fastest 35mm lenses were 'normal' lenses around 50 mm.)    Of course, there could be other reasons for chosing a different length of lens, such as perspective, or restrictions on how close or far you can get.

1: Regarding lens choice, some have said go wide and some have said go long. My understanding is that for equal magnification - i.e. for the same image size of the subject on the sensor - that depth of field is independent of focal length. I.e., put on a 100/3.5 and fill the frame with your subject, look at the DOF, then put on a 28/3.5, walk a lot closer until you fill the frame again, and look at the DOF -- my understanding is it should be roughly the same.

2: So, for maximum bokeh on a given choice of subject, just pick the lens with the smallest focal ratio (f-number) you have, put it on, and walk to where you need to be to get it the size you want in the frame. Usually that won't be your shortest or widest lens, but something in between. (Traditionally the fastest 35mm lenses were 'normal' lenses around 50 mm.)    Of course, there could be other reasons for choosing a different length of lens, such as perspective, or restrictions on how close or far you can get.

Typically lenses over 75mm (FOV) do better than shorter FL's.
I like using an adapted 50mm (100mm fov) and try to keep my subject within 6 feet.
I also use a .6 ND filter so I can use f/1.5 in bright day light.
I'd say with adapted lenses, 50mm to 135mm are good picks. with the longer ones at least f/2.8
The Russian 85mm f/2 in M42 mount sells for under $150.00, and is a Zeiss Sonnar design, known for it's creamy bokeh. Early models... 1950's or early 1960's

EDIT: 1-15-2011
On the Quoted 1st point:
This is correct. If you move the vantage point to have the same framing with different lens focal lengths. the DOF is similar at the same f/stop on the same camera format.

There is a Themed Thread here http://e-p1.net/photo-projects/wnw-%27bokeh%27-you-know-that-lovely-out-of-focus-area-show-us-yours/  to post your Bokeh" shots, after you have gleaned this tutorial thread.