I'll chime in with a starter budget:
Supercharger
You can get Jackson and Vortech Tune-it-Yourself kits at this price no problem, and Innovate Intercooled for a couple hundred more. You could probably get one cheaper if you ask around and/or kept an eye out for deals or sales and whatnot.
Tune
This $700 amount is probably going to be a little high if you plan to dyno-tune at a nearby shop, and will probably be a little low if you plan to do a remote tune since you'll have to pick up the ECUTEK kit.
Installation
You'll be installing this yourself on this budget, bub. The Innovate has a good reputation for ease-of-installation, and the Jackson instructions look stupid simple. The Vortech instructions scare me, but each to his his/her own.
Dual Catch Can
For catching blow-by oil and what-not. Consensus is that this is a must if you want a prayer of your supercharged car making it to 100k miles.
Boost Gauge
Gotta keep an eye on that boost. Over-boosting with a supercharger isn't a big fear, but you still need to keep an eye out for boost leaks.
UEGO Wideband
Gotta keep an eye on those AFR readings, you don't want to pull a nelsmar (I kid I kid).
Gauge Pod
Gotta put the pods somewhere
Scangauge II
This fella will let you see your intake temps, coolant temps, and oil temp. The oil temp is especially important because you didn't want to spend the cash for an oil cooler. You need to know when the oil is getting hot so you can ease off.
Optional: Engine Oil Cooler ($700)
Without an engine oil cooler, you are going to see massive heat soak in your engine oil after just 1 or 2 hard pulls. I did not originally include this because it puts your budget way up at $6500 and is a performance mod and not a reliability/safety mod
as long as you keep an eye on your oil temps and don't push a hot engine. Also, you can easily purchase this later and add it on after-the-fact whereas everything else is virtually mandatory from the get-go.
Obviously there is a lot of wiggle room here, it's just a starter budget for the noobs who come a'callin.