Well, personally from experience, a shop as in an in game shop is a great option, have spawn cages among other things to give a goal to work to. Also, challenges, if you use the Askyblock plugin, you can do a challenges, which give good items. The giveout items can be customized as well.
Another thing is some mob grinders, to allow players to earn money slowly.
There are a number of things that can cause minecraft to crash. The computer may have ram issues, your processor may also be causing the problem, it is 2.16ghz pentinum, the laptop does not seem to have a graphics card also (which is what is best for games) as it is a high performance processor. I recommend taking a look also at the crash logs, and posting them here. Could be a entity tick, or something funny.
Well, there is a few options but really, you need to update your version, first i recommend the spawnmob plugin (i cant remember its proper name) but it would allow you to spawn mobs, if you had a command sign or something hooked up to a pressure plate.
With spawn mob you can customise how many mobs you want to spawn, and many other things. Here is the link to the plugin for your reference. http://dev.bukkit.org/bukkit-plugins/spawnmob/