A strap around the bottom of the downtube holds a lot of crap- A tube, tire lever, glue and patches, a valve core, small plug tool and plugs, few baby zip ties, bit of duct tape. Stick your tube in a sock so it doesn't get fucked up. I'm using the Race Face strap, because it says Race Face on it.
A mini pump mounted next to the water bottle cage works for me.
Also I crammed a flat multi tool up out of sight under my saddle. Used the neoprene sleeve the tool came in and some zip ties to secure it. Bit rusty after a year or so, but secure and incognito.
As an aside: I've found that if you try to stash a chain breaker on your bike for some reason it takes up 1,000 times more space than a standard multi and is impossible.