I've found some new steamy patterns!
Butterick 5797 - Corset and shrug/bolero - I'm not really wild about the corset in this pattern. It's really short, so it looks more like a corset top than a real corset. But it might work if you want something more modern for clubbing and the like. The jacket on the other hand is really awesome, and I'll probably end up making it. I'll buy this pattern just for the jacket.
McCall 6615 - "Footwear Toppers"- The first thing I said when I saw this was "What the fuck are those?" I stand by that statement. However, one of the versions are actually shaped something like a spat for a high heeled boot. It has front laces. Have fun.
Simplicity 1780 - Misses Bolero Jackets and Vests. Yet another bolero pattern. But some nice options, like the vest (the one WITHOUT fake fur) and the short sleeve jackets.
Ok, that's mostly it from the major pattern companies. But I've found some neat free online patterns and sewing tutorials.
Favourite Frills Skirt - Free downloadable pattern for a very stylish modern office skirt with back bustle-y frills. Great for everyday steampunk.
Everywear Tails - Fantastic halter-style vest with tails.
The next links are to the fantastic (if defunct) Weekend Designer blog that offers guides to drafting your own patterns to your measurements. It has step by step guides to drawing the patterns and then assembling the items. Great stuff.
Double Breasted Waistcoat - A woman's vest that is pretty much tailor made for steampunk. I want to make this and I don't even need a vest, since I'm always in corsets.
Haberdashery Belt - A vest-style belt. I can see using this as a starting place for some corselets.
Custom Vest Pattern Drafting - Making a custom man's vest pattern.
Wide Brimmed Summer Hat - The instructions are for a floppy cloth summer hat, but could also be wired and covered in feathers and STUFF for a huge Edwardian hat.
Off-shoulder ruffled blouse - This could work if you want something fairly simple for under a corset. Maybe with a smaller ruffle, especially.