I don't wear a Camelback... mainly because I get really, really hot if my back is covered with it... I tried it once but especially in the summer here when I would need it, it was just too hot for me. I suffer in the heat and live for any weather that's from 40-80 degrees!
That being said, I have 2 bottle cages, a RoadMorph pump attached to my frame, and a medium size seat bag. The seat bag has 2 tubes, 2 tire levers, a multi tool, a ziploc with photocopy of my license and health insurance card, and a patch kit. I stopped carrying CO2 after getting the road morph... and switching to GatorSkins! Got tired of flatting...
I bought the Pearl Izumi jacket that has zip off sleeves... so if I get hot, I'll zip the sleeves off first and shove 'em in my pocket... if I need to strip the jacket I ROLL it up tight and it goes in one jersey pocket... my other pocket has cell phone, cash, and ClifShots... that's pretty much everything I need for about any distance... I mostly ride organized centuries... have only ridden 3 that weren't organized... but those routes always have 7-11's where I can get some food as needed... OH! And for a solo century... I also carry TP in my back pocket... I have had one emergency situation where I peed behind a shrub and really, really wished I had TP!
There is a fine line between "hobby" and "mental illness".