...one side to hold finished notes (either for immediate action, i.e, to use at the grocery store, or to transfer to my large index card box that holds reference notes)...
...and I store extra cards inside, in the middle of the case.
I really enjoy these cases. They are cheap and very functional. I can throw one in my purse and nothing happens to the cards or the pen. I love how I can grab the one I keep in my car and write a note at a red light. The surface is stable and the pen is always handy. Very low stress note-writing!
The blue one that I keep in my car, below (note the stack of blank index cards stored in the compartment above, along with a now-unused spiral-bound pocket notebook and my meter change purse), is described on the website as 'gel'. It's similar in feel to those soft, cushiony, cell-phone covers (vague, I know, sorry). Vinyl? Poly-something? Definitely man-made and most likely not biodegradable, so only buy it if you plan to use it for a long time (forever?)! I had my consciousness raised about these types of considerations after communicating via email with Rickshaw and asking them if they would use a piece of vinyl I have to make a folio (they allow customization of their products with your own fabric selection - hot!). Their response was polite and lengthy, and the answer was no. Very cool they took the time to educate me and plead the case for Mother Earth. One day I will get my hands on one of their cleverly-designed products! A little too expensive for me, right now, but I know quality doesn't come cheap.
You can find the note card cases at the links, below. I bought mine at Office Depot, so cheap!! Amazon also sells the black one, but it's twice as expensive as the ones sold at Office Depot.
Esselte At-Hand Note Card Case Holds & Includes 25 3 X 5 Ruled Cards, Black
Office Depot index card case, faux leather
Office Depot index card case, gel
BTW, I just noticed that the Office Depot link for the faux leather one says it is a 'stylish gel design', but it definitely has a different feel than the blue one. It is slightly stiffer and doesn't have the 'clingy' feel that the blue one does.