Nice to hear that you are willing to take a leap of faith and try Linux. As Jo5h has so nicely posted. The best linux for beginners in my opinion is Ubuntu. It has a very well managed GUI, and overall feel. Also, they have a lot of support for many different hardware configurations including wireless.
Now on to your questions. You wanted to know about java, adobe, and shockwave. I can tell you that java and adobe will run without any problem. I haven't really had on install shockwave yet so, I don't know so much about it, but I am sure that there is a way to do it, and that it should go relatively smooth.
Next AIM. There is a great program called Pidgin
that is a multi-protocal IM client. This is what comes standard on most major distros. So you should be fine there.
Last, gaming. There are a couple of programs that are out there that work well. One of the is call WINE
. This is a program that uses windows .dll files and runs windows games on linux. The other is called cross-over. This is a program that uses the wine program as a base, but adds a nice gui on top and a little bit more user friendlyness. You can look both of them up if you want.
As for builds for your laptop, just about anything will do. The nice thing about linux is that it will work with just about any hardware configuration. You might need to do a little configuring but it will work in the end. So I wouldn't worry too much about your laptop.
If you have any question, feel free to ask me, and I will do my best to answer your question.