For fireworks all done with standard AE, click on Dan Ebberts head at the top of the page then scroll down to:
Building a 3D Particle Generator
http://www.creativecow.net/show.php?page=/articles/ebberts_dan/particle_gen... comes with an aep, so you can swap in you own Photoshop genertated particles if you like.
It's 3D so a fly through is cool.
Also, Particle Illusion makes great fireworks:
http://www.wondertouch.com/default.asp
The SE version is a fully functional 30 day trial, not watermarked.