What do you do on those days with a horrible flat featureless grey/white sky, the scourge of all photographers

I am concentrating on landscape or urban photography, I know these days can be great for portraits.

How do you salvage these days ?

I know concentrating on details is one option.

Does anyone have any other ideas ?

Repeat to yourself 100 times...there are no bad days to photograph, there are no bad days to photograph, there are no bad days to photograph...

Different subjects lend themselves to different light, so look for those subjects whose forms are enhanced by the particular light. If you're working in flat light, work with subjects that have a lot of texture/contrast detail: Tombstones, streets, details of old buildings, deep woods, alleyways, etc.

Whatever you do, don't fight the light. Work with it. If we all shoot our pix at the agreed upon sun up and sun down, all our work would look the same. You don't want to be the same as everyone else, do you?

Although I know this probably won't work if you have a specific objective, but try switching to black and white film on those days. It draws more attention to your subject, especially for urban if you have longer exposure and allow everything besides your subject to be out of focus (it's been a long time since I've done photography so please excuse me if I'm forgetting terminology or not being as clear as I should be)

Dramatic skies and shadow effects may not work well on grey days,however they are great for textures of buildings and pattern. Try to increase the contrast at the post processing stage.Putting good skies in is tricky because the light never seems to match and always looks contrived.Soft shadowy light is great for weddings,but you need to watch the colour balance,either work in RAW or B&W.Strong shadows can be a pest for architectural work and plant photography,especially flowers.The colour can be enhanced using hue and saturation tools.Urban depression and squalor looks better look at Bill Brandt's work.

People. Cloudy days tend to be fantastic for portraiture, as the entire sky is one big light source. You get rather soft light, rather flattering light for portraiture. The family of angles of the light will be so large that facial imperfections will not be quite as apparent.

If you need to kick up contrast a little, there's always using a fill flash or what have you, but this is another option.

Don't shoot that day, if it's that much of a scourge. I simply use it to whatever advantage I can, either shooting something or someone outdoors while omitting the sky but taking advantage of the sky being one big softbox, or I use it as a backdrop like this shot I did at a cemetary:

http://img.photobucket.com/albums/v444/j...

I still don't really like it, but it's not a bad image after I tweaked it a bit in photoshop. I kept the detail of the momument, the grey/white sky was sort of like a high key backdrop - the image didn't turn out half bad, or at least it wasn't a total loss. There isn't really a whole lot you can do on days like that, so unless you're creative, you may as well stay home on those days.

You should look at other pictures that are taken on those kinds of days. If you try to think of it as a challange. Try to take a moddy photo. The best pictures usually comes when the sky is kind of overcast anyway because direct sunlight give off more harsh light and shadows.

That is the type of day I pray for for weddings....beautiful, diffused lighting. If I were not doing portraits, a nice graduated filter or post production like HDR ie: http://www.flickr.com/photos/perki88/233...

or even put in a more interesting sky from another shot
http://www.flickr.com/photos/perki88/243...

How about trying to bounce some light on your subject using either flash, reflectors or a combo of both.

http://www.amazon.com/Adorama-Collapsibl...

You can pick these up pretty cheaply from ebay as well, they're great fun.

Look into getting a graduated ND filter.

take black and white photos the contrast is great