what kind of brushes would you usr to simulate  movements. I'm creating a realistic cartoon with 3d tools but i want to give more life to the sword fights and i don't find proper brushes. i guess that some abstract brushes or natural forms such as smoke or lightning could be correct solutions. Any advice will be welcome.

I don't know of any special brushes, but you can draw some speedlines using a basic hard edged brush, or use the motion blur filter on select parts of your image.
You could use some kind of irregular star shapes for the impact points.
For this you can use any of Photoshops star shapes and change it to your linking by moving the points of the path. 

Hi Ichtos, to make the sword look like movement. If you draw several sword poistions going towards object then fade sword from first step and increase strenght till the last impact . That should look like force. Hope that helps you .

i'd work both ideas in to the peice... use the multiple images with motion blur to blend them in place...

retrocity

One method I like to use is to copy the portion of the element (in this case the sword) onto a new layer. Go to FILTER/BLUR/MotionBlur. Use the directional 'wheel' to determine direction (motion) of blur. Use the bottom slider to set how much blur you want on the element. Move the finished layer below the element (sword) layer, and offset to show desired motion. Use the blurred object's layer OPACITY setting to fine tune transparency. Hope this helps!

It depends what you mean by movement and what for. If you want Anime Type movement Draw the Character a Anime Character Change it slightly save as a brush and you can use that for movement. If you mean something like Speedlines than a motion blur is what you. Or a pushed Back Movement Effect go to Radial Blur Zoom 100 Quality Best. Or if you want a Rotating Planet with movement all you need to do is play with the light to get a shadow over effect or light effect. Or say you do want to move a planet to make it look like its spinning with continents going round make a duplicate layer and choose free rotate (Make many identical Layers for this option.) this is another good Method. For Sword Fights Draw a sword in the hand of the Character and duplicate the sword and hand layer and free rotate it.(Make lots of Layers and You may want to patch it up after the free rotate as this can lower the quality. At the end of the day its all practice makes perfect. I know you only asked for Swords But I thought more examples might help.

Cheers

Karl