Here’s a quick XNA 4.0 particle demo. It can use a custom texture or if no texture is passed, it’ll emulate point sprites by using a 1x1 similar to my previous post regarding SpriteBatch based lines.
Check out the source code and take a look for yourself.
[pro-player type="mp4"]/wp-content/uploads/2010/03/Particle2D.mp4[/pro-player]