How to make hair look less thin?

[Mononoke]

I haven't written here for a while, mostly because I cut my hair from around TBL to shoulder length, and kind of lost interest in growing it out.
However, now I have a question unrelated to length:
A few years ago my hair got much thinner than it used to be (I believe it's due to medications I've started taking at the time). Even at shoulder length it looks thin, even though it's 1b/1c (that is, it's not so straight as to look thin just because of falling straight down).
Is there any convenient (and non-damaging) way to make it more "puffy" while still keeping it straight (I know braidwaves might help, but I'd rather keep my natural texture at least some of the time)?

Thanks!

[Silverbrumby]

I put mt hair up in a very loose bun right on top just before its dry and this gives it lift at the roots and loose waves.

[ositarosita]

I use volumizing shampoo/conditioner

[Tangle or Curl?]

I second the bun on top of the head.

[Magalo]

Dry shampoo!! It's a miracle in a can for my stick straight, flat hair. Sometimes I use it on freshly washed hair just to give it some lift. :)

[Wisé]

I started using Snowy's Message Technique (http://archive.longhaircommunity.com/showthread.php?t=15976) recently and noticed that it gives my hair more body (without disrupting my curls too much which could translate to keeping your hair straight) than clipping, top bunning or anything else.

I don't know if it will work the same on your straight hair though.

[Migranny]

I third the bun on top of your head!

[Evening]

I have the same issue, I lost hair due to medication and it became a lot thinner. I started various products and techniques to try and add some volume to it.
I know a lot of people here are iffy about certain products because of what they contain, but I'll tell you what I use anyway in case.
I wash my hair with Schwarzkopf Push Up Volume shampoo and conditioner, then I use a henna wax treatment, followed by the Schwarzkopf mousse (but I use that because I have curls and it defines them more, so you could try without them). The more you use the more weighed down it will be. Then after it dries a bit I use a claw clip to clip at least the top of my hair up to lift it it at the roots, or I may clip all of my hair up lightly. I find if I do it lightly it doesn't press my hair down too much as it dries and it looks fuller.