It should come as no surprise that I like steampunk, since I've been working on a product integrating steam technology into d20 for quite a while now, which is finally shaping up and nearing completion. I don't generally use the term steampunk, because as noted elsewhere in the thread, it implies the sort of pessimistic, dystopian take on Victorian society seen in books like "The Difference Engine". My take, on the other hand, is more along the lines of envisioning how the rise of steam technology would mesh with a magical world and the normal elements of the heroic fantasy genre.
Steam-trains and Sorcery: A D20 System sourcebook giving rules for advancing a fantasy setting into the steam age. Designed to be fully compatible and balanced with core rules, and to work equally well whether it is the basis of a campaign or added to an existing one. It will include a full featured rule set on how to handle technology, both real-world and "mad", including how it combines or conflicts with magic, as well as new classes such as the Gadgeteer and Medic, new skills, feats, spells, prestige classes, and equipment related to the genre. It will also be packed with information on how to craft a setting using thse rules or update any fantasy setting into this era in a believable and interesting manner, and plenty of good ideas about plots, organizations, and role-playing options in such a setting.
For those who don't want magic and technology mixed, we also include information on using the book for lower-powered, non-magical campaigns.
After a long while of being the only one working on anything along these lines, it is interesting to see a couple of similar products appear as we are almost finished (Steam & Steel, and Sorcery & Steam, the one by FFG). Hopefully, this means that this is emerging as a sub-genre, and people interested in playing in such a setting will want to get all three books for the most options. Some healthy competition should be good for everyone.