One of the most famous pork projects that a Republican was asking for is the "bridge to nowhere".
TCS Transportation Program: Gravina Bridge
Some projects are requested so that more jobs can be created for a certain state, or to create a tourest attraction or speical monument, etc.
This is partly because someone in the sentate or congress wants to represent his state by getting his state more federal money.
Our representive was able to get some federal funding to set aside more land areas in our deserts as a wildlife reservation. As one example. Some of the projects are used to take care of real problems such as new highways and so forth, which are used by everyone who visits the state (also).
I personally support some pork for the state who got the most pork during the Bush years. That money would be used to build a big PIG MONUMENT in the heart of Texas.