Okay, I know some other people have mentioned this - and been voted down for it - but this has to be said: both free software and flash drives are terrible ideas for stocking stuffers on general principles.
Look, there are two reasons for this. The first is that any worthwhile gift has to be about the person you're giving it to. It has to be something THEY will appreciate. And, ideally, it should be something they wouldn't have gotten otherwise. When it comes to holiday shopping, even the friends of mine who are techies I wouldn't give free software or a data stick to. The ones who are into free software likely already have what I'd give them, and the ones who aren't would probably prefer something more non-technical, or more difficult to come by. It doesn't matter if you think it's cool - it's what THEY think.
The second is that, well, the gift should be something out of the ordinary. A flash drive is a basic computer accessory, and free software is, well, FREE. If it was software you created, then it would be worthwhile, as it was something you made. But otherwise, it would be like giving somebody a box of tissues.
If you're looking for gift ideas, be creative and stay away from the free software. If you've got a wine lover, give them a bottle of ice wine; if you've got somebody who loves the cute stuff, an interesting plush toy or the like. And if you absolutely have to give somebody software, make it something you created yourself or something that they would have to go shopping and pay for to get otherwise.
But if you go with flash drives and free software, the only thing you'll end up coming across as is some boring, thoughtless, self-obsessed cheapskate. Believe me, you don't want that.