The only one I can think of right now is "Do Dandelions Roar" by kyrene - http://archiveofourown.org/series/9194. It's a massely long, but extremely awesome series that has Dean disappearing for two years only to reappear in his early teens and memory issues among other things. It is Sam/Dean and has a few warnings such as non-con so be warned.

omgoodness, yeah, i actually read part of that a few months ago, but then it got a little too iffy for me, but thank you SO much for the rec! <3

The Wish Verse by disneymagics (3 multi-chaptered fics so far)

http://disneymagics.livejournal.com/2913.html#cutid1 (link to story 1 in wish verse)
Summary: Sammy has just figured out that life isn't fair for his older brother, Dean. He wishes there was some way he could help. When his wish comes true their lives are changed forever. AU hurt/sick!Dean protective!Sam Wee!chester

wow, thank you so much! this sounds like exactly something I was looking for. I really appreciate it :] <3

Small Clause Out by authoressnebula
Summary: This was it. The only shot they really had to break the deal, and it still sucked. The boys find a way to break the deal, but the Dean that Sam'll be getting back's going to be a little bit...smaller.
This is NOT one of those fics where Sam winds up being Dean's big brother. Please hear me out on this. This is a fic wherein the boys have one last option to get Dean out of the deal, but there's still a small sacrifice that has to be made.
http://authoressnebula.livejournal.com/637715.html

Arrested Development Verse by Beth Summerson

Arrested Development - http://beth-summer.livejournal.com/4876.html
Summary: An AU story where Dean is at Stanford with Sam, relying on his brother to take care of him. Told from multiple outsider perspectives. A different take on the de-aging trope.
Trapped in Neverland - http://beth-summer.livejournal.com/5198.html
Summary: Despite all the moving around and the hunting and the constant training, Dean knew that he had one big responsibility: Take care of Sam. A prequel to the author's previous story Arrested Development.
The Classics Never Get Old - http://beth-summer.livejournal.com/5825.html#cutid1
Summary: As they were growing up and travelling on the road, Sam knew that one thing would never change. No matter what, Dean was his older brother. A continuation to the author's previous stories Arrested Development and Trapped in Neverland.

Oh and I almost forgot *facepalm*...

You Gotta Be Kidding by lampido (de-aged!bobby & de-aged!dean)
SUMMARY: She was a very dangerous witch, Sam said. Her grimoire is a very dangerous book, Sam said. Don't touch it, Sam said. Trouble is, Dean's been thinking with his Downstairs Brain again. Now Bobby is using the word 'idjit' with extreme prejudice.
http://www.fanfiction.net/s/7335583/1/You_Gotta_Be_Kidding

thank you so much ((for both your posts!)), i really appreciate it! <3

OMG! You have to read this one!
From Hell (Or Thereabouts) He Came by The Huntress
Summary: A witch casts a spell over Dean - Spoilers: Season 1
Rated: NC-17
Genres: Angst, First Time, Humor, Hurt & Comfort
Chapters: 8 Completed: Yes Word count: 22799
http://www.sinful-desire.org/archive/viewstory.php?sid=1600&warning=5
This is an amazing story, I laughed so hard in some parts and wanted to cry in others.
I hope you enjoy it! *hug* halliwitch

thank you so very much! :] <3

• Have Yourself A Merry Little Xmas 1/4 - An elf grants Sam a wish & de-ages Dean http://eloise-bright.livejournal.com/126400.html

• Back At The Beginning With You - Dean is de-aged to 12 & John dumps him on Sam http://dolimir-k.livejournal.com/697610.html

• Cotton Candy And Skinned Knees - Sam must look after a Dean in a 7yr old body http://tabbyshhh.livejournal.com/514.html

• Starting Over Verse http://iamstealthyone.livejournal.com/tag/starting%20over%20%27verse

• One Week - For 1 week Sam has a 4 year old brother, can he survive? http://supernaturalfic.livejournal.com/5529120.html

• To Be Young Again 1/6 - Sam learns about Dean when Dean becomes a kid again http://melodious329.livejournal.com/9647.html

• What's My Age Again 1/3 - Sam accidentally wishes Dean was the younger brother http://usmc75.livejournal.com/697497.html

• Herding Angels - Sam's stuck looking after 5yr old Dean & Cas http://kasmodia.livejournal.com/16763.html

• Something Obvious - Angels make Dean a 5yr old in the belief he'll say YES http://rainylemons.livejournal.com/7093.html

• Eat Me, Drink Me - Sam & Bobby watch over a 4yr old Dean who won't speak http://zoemathemata.livejournal.com/tag/deaged%21dean

• Little - One day a year Dean is cursed to become 5 again http://kellifer-fic.livejournal.com/257469.html

• This Is Heavy - Dean becomes a 7yr old & Sam must tell him Dad's dead http://ghostwriter056.livejournal.com/10258.html

• Snot Funny, Sam - Dean's been de-aged to 4, & has a cold http://roque-clasique.livejournal.com/41112.html

• This Is How They Survive -Dean is de-aged to 4, but he remembers Hell http://el-spirito23.livejournal.com/4955.html

• Something Good -Dean's de-aged to 4 & Sam's gonna give him a childhood til http://norahy.livejournal.com/63398.html

• Fortune's Son - Dean's been de-aged & Sam gets a hint of what his life was like http://salacious-newt.livejournal.com/6233.html

• 1~So Remember Then - Sam-16, Dean de-aged to 4, John walks & leaves Sam to cope http://mimblexwimble.livejournal.com/tag/innocence%20%27verse

whoaaaa SO MANY thank you hon! <33

I can't believe this classic of the genre hasn't yet been recced!

Under a Haystack (http://archiveofourown.org/works/10450) by janissa11

thanks! :]

Ten and Taken (http://www.fanfiction.net/s/5060556/1/) by sg2009
Summery: Sam protects his de-aged, obnoxious, traumatized brother.

And a shameless self-rec if you don't mind.
Nothing Else Matters (http://www.fanfiction.net/s/7923985/1/Nothing_Else_Matters)
Summery: Ten year old Dean gets kidnapped. He escapes. End of story? Of course it's a little more complicated than that.

ohhh these sounds awesome! and self recs are totally cool in my book. thanks a ton! <3