Here’s what i took on my bike ride yesterday:
Nalgene bottle
Camelbak bladder*
Lock*
Fruit*/balance bar
Dslr w/ polarizer in camera bag
Small towel*
Pen*
Small notepad*
Bike jersey
Sunblock*/chapstick*
DPOA (always)*
Wallet*
Invisalign case*
Bike seatbag w/ tools*

here’s what i considered adding to the aforementioned list but rationality won out and they were left at home:
Book
Bike pump
Tube
Journal

And here’s what i didn’t use:
The lock, the jersey, the towel, the balance bar, the nalgene bottle, and the sunblock (i pretreated and no further application was necessary)

Here’s what i wish i had:
A basket or rack to carry all my crap

* denotes items brought on today’s ride, along with the following:
Book
Large towel to keep my behind from getting sandy
iPod shuffle (because my iPhone just isn’t enough…)
Point n shoot camera
Flip flops
A nylon bag to keep my bike stuff from getting sandy and for the baguette i’m going to buy on the way home

I considered bringing sunglasses and realized that was overkill. And i again considered the journal but left it at home yet again.

Here’s what i wish i had:
The bike jersey (it’s chilly). Scratch that. I wish i had a jacket and some pants. And maybe my fuzzy squirrel hat.
A basket or rack to carry all my crap (always)

And here’s what i didn’t use:
the small towel (no big deal, it isn’t too big or too heavy and could be verrrrry handy in the right conditions, like, say, a bloody nose)
the iPod shuffle (ok, fine, next time i’ll leave it at home. sheesh.)