Carrying stuff with you on long rides

[GingerbreadGirl]

...seat bag for tube and tools and cell phone and in this heat I have been wearing my running tanks instead of jerseys (don't have a sleeveless jersey yet) so I've been carrying a tiny drawstring nylon backpack. I freeze my second water bottle and throw that in there so my back doesn't get hot, and have my id and a snack in there. A shot blok or maybe one of those packed lunch-sized potato chips.

I am trying to figure out how to squeeze another water bottle onto my road compact... do those cages with the velcro strap really stay on? What if I reinforce with zipties?

[indysteel]

...seat bag for tube and tools and cell phone and in this heat I have been wearing my running tanks instead of jerseys (don't have a sleeveless jersey yet) so I've been carrying a tiny drawstring nylon backpack. I freeze my second water bottle and throw that in there so my back doesn't get hot, and have my id and a snack in there. A shot blok or maybe one of those packed lunch-sized potato chips.

I am trying to figure out how to squeeze another water bottle onto my road compact... do those cages with the velcro strap really stay on? What if I reinforce with zipties?

I assume you already have a cage on the seat tube. Will another cage not fit on the downtube? I have a Bontrager cage on my MTB's downtube that offers a "side entry." If a standard cage won't work, you might try something like that.

[Biciclista]

first you need a lightweight rack on the back of your bike. You can hold all sorts of things there, including panniers, booster seats, etc. And you can get a little bag that ties on the back of your seatpost as well.
Another possibility is to get a little bag that hangs in front of your handlebars. Hm, I have all of that sutff.