Jujutsu styles emphasize "soft" techniques, meaning that they do not oppose attacks head-on, but rather redirect the force of the attack. However "soft" the technique may be, however, the end result is usually broken bones or dislocated joints. Ueshiba refined jujutsu techniques to give practitioners the option of neutralizing an attacker without serious injury to either party. Naturally, to end a combat without injuring one's opponent requires skill in execution, courage enough to avoid harming one's adversary unnecessarily, and calm enough judgement to make that determination under stress. Ueshiba's accomplishment was to develop a system that, with dedicated training, could realize this ideal.
Aikido at Wikipedia - an excellent overview of the art.
Kaiju Aikido Club - the club in Santa Fe where I practice aikido under Nakamura-sensei.
Aikido Hombu Dojo - the home organization of Aikido in Japan, with which the ADI is affiliated.