Harry Potter
The Fourth Year by Caligryphy -- Harry/Snape, first time, mentions of mpreg. What if after the war, Snape was deemed by the Ministry of Magic to be dangerous and not allowed to work or be in public? Basically he's under house arrest and Harry is his 'guardian.' So, we get to see Hogwarts' former Potions Master become Harry's live-in housekeeper. No, really. He smokes, clean the house, watches soaps and moans about everything. It is Snape as the Very Unhappy Housewife of Harry Potter. *g* It's funny and extremely romantic at the same time.
Caligryphy is able to blend humor, the perfect Snape voice and Harry's growing infatuation with his former professor into a wonderful story that has quickly become one of my all-time favorite Snarry stories.
A Convenient Marriage by Diana Williams -- Harry/Snape. Eventual mpreg. A forced marriage makes Harry and Snape reconsider their preconceived notions about each other.
A Nick in Time & Growing Pains by Tiranog -- Harry/Snape, Ron/Hermione. Harry and Snape are transformed into children in the first story and learn to enjoy their childhoods (no sex in the prequel). In Growing Pains, Snape and Harry are no longer children and must deal with their feelings for one another. A beautifully written series that hits all my buttons.
Nocturne by Tiranog -- Harry/Snape. Set after the war, Harry is an adult and Snape is a vampire. Yes, I thought that would get your attention: Vampire!Snape. Harry and he come to an unusual arrangement, Harry will be Snape's 'blood donor' and in return, Snape will satisfy Harry's sexual needs. But, as with all Tiranog's stories, this arrangement takes a turn into something more than fuck buddies as Harry begins to care for Snape. Amazing characterizations and hot, sensual scenes will leave you panting for more.
Reunion & Name Dropping & Trial and Error & Small Towns & My Bloody Valentine (WIP) by Icarus -- Ron/Draco. Eventual mpreg. A delightful series that starts with Draco showing up on Ron's doorstep ten years after Ron and he have broken off an affair. Draco has something up his sleeve and it isn't his wand! He wants Ron to have his baby, as he needs an heir, but is there more involved?
Coils of Gold by Crymsyn -- Harry/Snape, Ron/Draco. A/U, BDSM, mpreg (R/D). Two of my favorite pairings in one story - yummy! This one has Ron and Harry kidnapped and virtual sex slaves to Snape and Draco. It is not my usual cup of tea, but it is so well-written, give it a chance, you might find like I did you secretly enjoy it! Snape is the new Dark Lord and all he wants is Dumbledore's defeat and Harry in his bed and not necessarily in that order! Issues of non-con and D/s roles, but deep down Sev loves Harry and Draco worships Ron. An interesting take on what could happen if fan fic authors took over J.K. Rowling's world!