Finally, I got a mini-softbox you Velcro onto your flash from Fotofile@MBK and it cost a fortune, something like 2400 baht or so. I doesn't soften the light at all. It's pretty much useless.

Unfortunately I found most of these devices don't do much to change the light from an on camera flash. I use one of those Stofen Omni Bounce units (
http://www.stofen.com/store/omni.asp) on my flashes and tilt the flash up at a 45 degree angle to reduce the directness of the flash. If you are shooting in a low ceiling area you will get a bit of bounce from the ceiling too when pointing it up.
I have also seen a number of inexpensive copies of the Stofen design selling in camera shops around Bangkok and they even make some of them in different colors too as a color filter. Bear in mind though that all of these things reduce the power of your light by a stop or two so you will need to compensate for that.
If you really want to improve contrast though, and reduce flatness of the light coming from the flash, you are going to need to use the flash as a remote slave from the side of the subject at an angle of at least 30 degrees off the camera in order to increase contrast at all.
The bottom line is, even if you do something to soften the light with an attachment, you are not going to gain any contrast or moodiness in your lighting unless you change the direction of the flash from being exactly from the same direction the camera is shooting from. Meaning, you have to get the flash off of the camera for the light to really look any better.
I hope that helps and this is probably something that is never explained when they are selling all these flash attachment gadgets.