Here is how I made the clouds for my Cloud Hopping picture, as requested by Lance.
Please bear in mind that the settings I use here is purely a guide. You will probably come up with something completely different.
Only one plug in is required for this tut . Ed Harvey`s Dents. -
http://forums.getpaint.net/index.php?/topic/11520-ed-harvey-effects-v336/ (now incorporated into PDN - thanks Lance for mentioning that.

)
Anyway , lets get started.
First you will want a nice sky coloured background. I used 8cc2ff foreground and cfecfe background but you can used whichever you prefer.Then just add a linear gradient to get something like this. -

Next, on a new layer, you want to make a white ellipse -

Now use Dents to get a `jelly' look . Play around with the settings until you are happy. I used Scale - 85, Refraction 13. The rest I left at default settings. You can do it more than once if you wish using Ctrl-F. For this tut I repeated it once. You should now have something like this -

New layer, select the cloud using the Magic Wand and on your new layer draw a light grey line along the bottom of the cloud. I used bcbcbc for the grey in this one.

Deselect and use Gaussian Blur . I used 35 as the setting but it will vary from cloud to cloud. You want to end up with something like this -

Merge your two cloud layers.
Next it`s back to the Dents for the fluffy look . I used these settings -

Use a transparent gradient as to blend the cloud in . I find using a radial gradient works best and gives you more control. You should end up with a nice fluffy cloud -

Then just duplicate,move and use transparent gradients to blend them together like so -

For the best effect you should repeat the tutorial a number of times with different settings to get different shaped clouds each time. After all , when did you ever see two identical clouds?
And that concludes this tutorial. Enjoy.
