I remember when it seemed like every 2nd bike you saw had a frame bag strapped under the top tube/seat tube join.
As well as providing some limited storage it was also used for carrying your mountain bike on your shoulder if you every tried to actually go up a mountain on it and discovered that, actually, walking was easier.
Browsing the Alpkit website (good kit at great prices IMO) I came across the "Stingray"
http://www.alpkit.com/shop/cart.php?target=product&product_id=16786&category_id=324
Pretty cool idea. You essentially send Alpkit a template of what you want and they'll make the bag for you.
I'm aware that some CCE-ers have the skills to do this kind of thing themselves so perhaps they can comment on the fairness of the price.
I'd actually like a very small one of these to fit the small triangle in a Birdy frame - I wonder if they'd do a discount for very small bag?
Edit: Also, this 'beta release/failed concept' tent in the Clearance section looks quite intriguing:
http://www.alpkit.com/shop/cart.php?target=product&product_id=16865&category_id=282