You can go to a temple and have the priest there cast Raise Dead on the corpse. There is a temple right there in the Friendly Arm Inn. It will cost you 100g for this service. There is a chance that the Raise Dead spell may fail if the victim's Constitution isn't really high (below 15, I think, check the manual for exact values). Also, a corpse is required for the spell to work, so if the victim has been 'chunked', then raising them will be impossible (if their picture is merely grayed out, then they are raiseable, if it has totally disappeared then they are perma-dead). Lastly, casting Raise Dead on someone reduces their Constitution by 1, even if totally successful (95% sure it happens every time, but it might just be a random chance for this to occur).

EDIT:
Apparently, I was wrong on the price. I just double-checked a FAQ and it said it was 2,000g at neutral temples (the one at the FAI is neutral), but if you have an opposing alignment (say if you are evil and try to use the one in Nashkel) then it can be as much as 10k gold. I could have sworn it was only 100g when i played through though, maybe it was some mod I was using.

Also, Con stats for resurrection survival:
3: 40%
4: 45%
5: 50%
6: 55%
7: 60%
8: 65%
9: 70%
10: 75%
11: 80%
12: 85%
13: 90%
14: 92%
15: 94%
16: 96%
17: 98%
18: 100%