1. The were-panther(s)
Remember Hotshot in the show, the town with all the druggies? Well in the books, Hotshot was a town full of hard workers. They were, in fact, were-panthers. Remember when Jason was taken and bitten? Remember how he DIDN'T turn into a were-panther? Well...he sort of does in the books. He is really like a human-panther hybrid monster.
2. Bill's software
Bill devotes a lot of his time to this software he creates. The software is like Wikipedia of almost all the vampires! It tells you their maker, their progeny(ies), when they were turned, when they met the true death (if they have), and where they reside.
Bill's software leads into the the vampire convention known as Rhodes. It was a huge meeting of the minds in the vampire world at this swanky hotel. Well, long story short the hotel blows up. Someone tried to kill the vampires inside (theres like a billion in there). Well, Sophie-Anne Leclerq loses her legs during the explosion.
4. Bill: King of Louisiana?
No, just no. After Sophie-Anne's death, Bill does NOT take over.
5. The were-tiger.
Yes that's right, a were-tiger. His name is Quinn. He coordinates events for "supes" (think vampire weddings). He lasted a few books, and was one of Sookie's many supernatural suitors.
Lafayette gets killed early on in the series. Thankfully they kept him in the show though!
7. Godric...do you mean Godfrey?
In the book Godric is actually named Godfrey. And no, he is not Eric's maker.
8. Who is Eric's maker then?
Three words: Appius Livius Ocella. A vicious, ancient Roman who turns princes into his progenies. And Eric has a brother, Alexei Romanov. THE Alexei Romanov. (He's nuts).
Elvis lives on my friend. His name is now Bubba, and drinks cat blood. Do not call him Elvis or ask him to sing or he will flip out and kill you.
10. Arlene, the bad guy.
At one point Arlene attempts to lure Sookie to her death. Some friend she is!
11. JB du Rhone
Sookie's handsome, yet dumb friend from school. He marries Tara and they have twins. Also, Tara owns a clothing store called "Tara's Togs" and never becomes a vampire.
There are countless other things to add, but I won't take up your entire week to tell you.
Be sure to watch the *sobs* series finale of True Blood on HBO, Sundays at 9/8c.