I just recently bought Dragon Age Origins and am have a lot of fun with it. I have 800 points on LIVE and I was wondering which would be the best add-on to buy? I know a couple of them are 1200 points, so they're out, but what do you think is best that is under 800?

Which ones do you already own? Did you receive the free Shale companion code? If not, that's definitely the one to go for. Otherwise most of them range from pretty ''OK'' to ''just terrible''. Minus Shale, the only other one worth investing towards is Wardens Keep or Leliana's Song.

I don't own any yet, so any of them are options. 

Shale is $15. But if you bought the game new then it was included. 

Shale is 1200.  
 
Go with Warden's Keep. 

I got the Ultimate Edition for PC which has all the DLC two weeks ago. 
 
So far none of the DLC parts are actually compelling (Haven't played Awakening yet since I'm still in the process of beating DAO).  
 
Very short, not a lot of story, and the rewards are weak (I expected a full castle in Warden's Keep, not just hanging around outside. BG2 just straight up gave you a castle early on and had a bunch of micro-manageable features). 

I really like Warden's Keep

" Shale is 1200.   Go with Warden's Keep.  "

I heard Leliana's Song Is really good but, if you don't have Shale it might be worth spending another 400 points, she is really awesome. If you can be Awakening online you might also want to spend a little more and get it.

I really liked Return to Ostagar for the closure it gives to that sub-plot.
Awakenings isn't bad at all, although it'll probably exceed your budget as hinted above (I'm on PS3 so not sure about Live points).
Haven't gotten Shale myself, might do that sometime.

" @N3onThr33:  I would've actually recommended just picking up the ultimate edition of DA:O since you get everything for not much more than Awakening on it's own. I actually ended up getting the ultimate edition on PC even though I already owned Origins, and the first three DLC packs. It was only $10 more than Awakening on Steam, so I figured it was worth it to get the remaining three DLC packs for a discounted price. "

Great advice!

If you don't do that and are not in a rush I know I saw the DLC super cheap before DA:2 came out, maybe they will bring it on sale sometime soon. $15/$10 seems a lot to pay for some of that stuff. Warden Keep I just did but wouldn't pay $10 for it personally.

Your best bet might be sell your copy on half.com or ebay, then pick up the ultimate edition, I got mine new for $40 and it includes awakening which I havn't played but heard is pretty long in itself.