There is a huge range of robo!Sam fic out there; this is just a sampling of my personal favorites, fics that draw on the parts of the robo!Sam arc that particularly resonated with me.
Long Distance by
jukeboxhound Gen, PG-13, c1.1K words
I love a good voicemail fix-it, but I also love this fic, which doesn't fix anything.
For a season there must be pain by
britomart_is Sam/Dean, PG, c1.2K words
One of the best things about the robo!Sam arc to me was that robo!Sam was to some extent an independent character with his own tragedy. This fic is a gut-punching development of that potential.
The Perfect Animal by
obstinatrix Sam/Dean, NC-17, no wordcount (it's short)
This, too, touches on the tragedy that robo!Sam was for robo!Sam, not just for Sam and Dean. It's also hot porn that takes a complex view of robo!Sam's sexuality.
The Greatest of These by
wanttobeatree Gen, PG, no wordcount (short)
Written before canon resouling, this is still my favorite alternate take on Sam getting his soul back, a gradual, sometimes painful, strangely low key but utterly satisfying process.
since feeling is first by
queenklu Sam/Dean, NC-17, c14.5K words
This takes a different approach to resouled Sam than most fic I have read: instead of focusing on Sam's guilt over robo!Sam's actions, it looks at the aftereffects of the part of robo!Sam that needed Dean to tell him what to do and how to behave. The holdover of those aspects of Dean's relationship with robo!Sam into first time wincest with resouled!Sam is a fascinating dynamic. Plus, lovely curtain!fic.