I'lll just put this link here.
It has an incredibly comprehensive Magitech system, along with a little bit that could help connect it to other steampunk stuff.
It allows for almost all magitech devices imaginable, including a magic missle chain-gun, and mecha, skyships, and smart missiles, and adds a few spells to make "common" devices a bit easier to make. It even has rules for collisions based on the relative Kinetic energies to the two objects (ie, real physics, tweaked slightly to fit in D&D).
A Few quotes.

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Quote Originally Posted by Welknair View Post
Battery ----> Tapestry ---l--> Runestone of Scorching Ray

Sorry, did I just make a Ray Gun?

Large orbital platform, containing massive batteries, a series of powerful Tapestries feeding Transit Stones, aimed towards a central Epic Runestone containing a modified version of Vengeful Gaze of God, one with a longer casting time, no XP cost, and requiring large numbers of participating casters. Sorry, did I just make a Death Star?

Flame Blade - 3 - 1 minute/CL - As Flame Dagger (from the Spell compendium), but 1d8+CL (Max +15) and the blade is the size of a Longsword. And if you attach this to a casting device... Sorry did I just make a Lightsaber?
Quote Originally Posted by Welknair View Post

Fabricate. Sorry did I just make a factory?

Create Thrust Sorry did I just make a Rocket Launcher?