>> I currently have a 55 gallon aquarium with one 48" 40 watt Triton bulb. 
I am looking to increase my lighting by possibly building an inexpensive hood.
Does anyone have any suggestions as to how
to set this up and how many tubes to use? <<

Several ways depending on what you want.  You can simply replace the current top
with glass tops and set two light strips on the back, or buy a dual strip light
and do the same thing.  If you want a full canopy and want to build it yourself
it's easy and inexpensive.  I spent 30 bucks, excluding lights, to build mine.
There are plans on the Krib somewhere, or if you'd like email me and I'll send
you some.  Mine holds up to four standard 48" fluorescents.  How many you will
need/want depends on CO2 or not, and what plants you wish to plant.