We R Memory Keepers and Fancy Pants also make similar products where you can use them for photos instead of full layouts. Or mini layouts or tags...whatever you want to put in them. They are 4x6 though.
I have seen some out there with smaller sizes, but can't find them lately. Grr...
I am not going to put the link, but the place I order from that I have found the best selection and prices is a place called c-line products. If you do the www and then c-lineproducts and then the .com it should come up for you.
They aren't necessarily acid free, but I have been contemplating using baseball card protectors. They are the perfect size for tags and ATCs. I saw an album that someone did a few years ago in an lss. I LOVED it. She had done a bunch of cute tags since those were so trendy then, but the tags had photos or journaling and stuff. Instead of making a whole layout around the tag or trying to get the tag on the layout...she had page protectors that size and she just slid the tags in like they were a ton of mini pages, but on one 12x12 page protector. I liked that idea. I also have been having fun making ATCs with some friends here at sb.com and I want to save them in my album, but I don't want to stick them all on a layout so that would be cool for it.
There was also a class taught at my lss where they cut up the smaller ones like the page protectors that hold little sticker sheets. Then they used a strip of that and stuck various elements in it and attached it to the page...it was a cool way to add something different to a page.