This is the site you need to visit http://answerspot.blogspot.com/2006/06/complete-list-of-online-casino-bonuses.html

70+ casinos and over $18,000 in bonuses.  Many require no deposit at all to get some free real money chips!  This list has the casino name, bonus offer, and software used.

The best software question is subjective.  You mentioned "cartoon" machines.  There are several "Marvel Comics" themed machines at Cryptologic software casinos.  (Silver Surfer, Blade, Thor, X-men, The Punisher)  InterCasino and VIP Casino are two Cryptologic casinos on that bonus list.

My other top choice is Microgaming software.  All around, this software may be the very best.  They have tons of awesome slot machines with cool 2nd screen bonuses.