Hrm, Check the relay for the fuel pump... see if it is getting hot, and pull it out to see if the plastic on the bottom near the relay's terminals are melted at all.
If so, could be the relay going bad, or a good sign that your fuel pump is going bad.
If you haven't had it replaced, you should replace your fuel filter just to rule that out.
Otherwise, it is probably your fuel pump. To test it, you can obtain a fuel pressure gauge and test it. I don't remember the spec's or how to test it right off hand. There's a test-port on the fuel rail, it looks similar to your tire's air valve, but bigger.
This sounds so familiar to my problems, so I'd bet it is the fuel pump. Make sure you get a QUALITY fuel pump, though! I went through 3 in 4 years with my '94 Explorer after the original one went bad after 150k miles. If I remember correctly, the 3rd one I got installed in a Ford service center, so it was an OEM part and it lasted the longest out of all the replacements (sold the truck ~2 years ago, so don't know if it is still going).
---edit:
When my fuel pump started to go bad, sometimes it would start, sometimes it wouldn't, and sometimes it would chug. It usually wouldn't start easily after driving it and parking it for a "short" period of an hour or so.
Oh... and one way to test if the fuel pump is somewhat working is to turn your ignition forward to the "accessory" position (Key-on, Engine-off), and you should be able to hear the pump turn on briefly - it's easiest to have two people do this, have one near the gas tank to listen. Though, you'll still hear it if the pump is going bad but is getting weak.
---edit 2:
The Fuel Pressure Regulator could be to blame too, but I don't know much about that.
---edit 3:
If you read through the previous posts in this (my) thread, you'll see I said basically the same thing everyone else in this thread told me - but they say it better. lol.
