I started cycling several years ago, and found that having a Bento Box attached to my road bike was a necessity. Cycling clothes do not generally have many pockets, so having the small things I need to access on a long ride is important.
A Bento Box is a small box (5.5" x 3.25" x 1.5") made of nylon that attaches to the top tube of your bike, right behind your handlbars. It is attached with velcro so is easy to remove if need be.
It is roomy enough to put your keys, cell phone, money, power gels or bars, band-aids, lip balm, and the ever-important ibuprofen. It has a mesh top, so you can see inside without removing the top (nice when you are receiving a phone call and you don't want to take out your phone to see who it is). The sides are soft so they do expand to fit what you need, but they are reinforced it doesn't collapse.
I would highly recommend a bento box for anyone who loves to cycle.