www.homemadeturbo.com is your friend
edit: you beat me to it lol
well ill start by asking you what motor/car you are starting with. It is much esier to build a cheap kit for a d series because you can use more junkyard parts:
for a D series general junkyard turbo setup:
Manifold - Civic HF/STD/CX exhaust manifold and adapter plate from a place online for your specific turbo (manifold $25, adapter $50)
Turbo - any dsm turbo (14b, T25...) saab or volvo t3 ($50-150)
Downpipe - muffler shop make you one ($50-$100)
Intercooler- Dsm sidemount or starion/conquest for a frontmount (25-75)
IC piping - Misc rubber ic piping or make your own w/ss or mild steel (20- 100)
BOV - DSM 1g bov or you could buy an ebay one (25-50)
Oil lines - stealthmodeperformance.com kit (75)
Misc water/vaccum lines- napa (20)
Injectors-DSM 450's (50-75 depending on what OBD you are and if you need resistors)
Uberdata/Turboedit - free (read up)
that totals to about $390 to $725 depending on what kind of deal you get and how ghetto looking you are willing to make your kit look to save a buck. I might have left something out you might need, but that pretty much sums up your total kit plus engine management and everything you need.