Here are a few of my favorite series...
Adult:
"Lords of the Underworld" by Gena Showalter (PNR)
"The Black Dagger Brotherhood" by J.R. Ward (PNR)
"Immortals After Dark" by Kresley Cole (PNR)
"The Fever Series" by Karen Moning (UF)
"Night Huntress" by Jeaniene Frost (UF)
"Sookie Stackhouse" by Charlaine Harris (UF)
"Midnight Breed" by Lara Adrian (PNR)
"Shifters" by Rachel Vincent (UF)
"Demonica" by Larissa Ione (PNR)
"Downside Ghosts" by Stacia Kane (UF)
"The Stark Trilogy" by J. Kenner (contemp.)
"The Crossfire series" by Sylvia Day (contemp.)
"Inside Out" by Lisa Renee Jones (contemp.)
Young Adult:
"The Twilight Saga" by Stephenie Meyer
"The Mortal Instruments" by Cassandra Clare
"Vampire Academy" by Richelle Mead
"Vampire Diaries" by L.J. Smith
"House of Night" by P.C. and Kristin Cast