Sativus:
a bit of advice on "which strain for me," type thread I highly recomend you have some specifics of what your looking for. There is a wide variety in the "sativa" genepool with a widerange of effects, also what smokers consider "sativa" from a bag of nugs is highly subjective and based off of stereotypes quite often. posting what you want as far as flowering time is a good idea as well.
The sativas that people tend to list as top sativas are as follows: Super silver haze, C99, Kali mist, jack herrer, haze, flo, f13, super silver diesel haze, afghan haze, mango haze, mexican haze, love potion, titans haze, nl5xhaze, sweet skunk, colombian gold, punta roja, colombian black, thai, oaxacan gold, acapulco gold, zamal, highland nepalese, malawi gold, panama red, satori, highland mexican.
I think its a safe bet to get something from that list and be satisfied.
also for landraces check reeferman, Ace seeds, and the real seed company.