Thanks to PingKiller for the URL's

API - http://www.eveonline.com/api/
EFT - http://myeve.eve-online.com/ingameboard.asp?a=topic&threadID=548883%3C
EveHq - http://www.evehq.net/page.php?3
EveMon - http://evemon.battleclinic.com
InEve.Net - http://ineve.net
Eve-Sheet - http://www.eve-sheet.com

Damages Encountered (By %); Tailor your resists to optimize;
For L4 Missions:

Gurista/EoM: 75% kin | 25% therm
Angel: 70% exp | 20% kin | 10% em
Sansha/Blood/Amarr: 50% em | 50% therm
Serpentis/Caldari: 50% kin | 50% therm
Gallente: 50% kin | 40% therm | 10% em
Minmatar: 50% exp | 20% em | 20% kin | 10% therm
Mercenaries: 50% therm | 30% kin | 10% exp | 10% em
Rogue drones: 70% exp | 20% kin | 10% therm

Note that some npcs do not follow this trend, e.g., Elite Drone Parasites, Gist Seraphim, etc