Allivymar,
You're in luck my friend

lights and cheap is something i've done a good deal of research on.
For your 55 gallon, option one...
www.reefgeek.com
Get a fulham workhorse 7 ballast - $36
Get a pair of 6700k power compact 96 watts - $40
Get a two power compact sockets - $8
Get a two pair of bulb clips - $8
For around $100 with shipping, you've got 192 watts of light.
Of course, you will need to figure out how to get these bulbs into your existing hood... if it is plastic than forget about it, and you will have to build a simple wood one. Plastic won't take the heat very well.
For your 55 gallon, option two...
Lowes (cheaper than
HD on lighting)
get two Sylvania 2x59 electronic ballasts - $50
get one "el cheapo" shop light - $7
get a two pack of sylvania daylight deluxe bulbs - $5
Open up your el cheapo shop light and throw away the ballast that is in there - or save it for your 10 gallon
Wire your two new ballasts in, one to each socket. Each ballast will have a pair of "leads" designed to run two bulbs, but instead, combine them to run a single bulb. This will double the output going to the bulb, making it considerablly brighter.
Put the shop light back together, load in the bulbs, and lay it across your tank - you now have approx 220 watts of light for under $70. Of course, running those bulbs at higher output will consume them faster, look to replace the bulbs after 4-6 months, but they are only $5 for a two pack, so not bad!
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For your 10 gallon...
Home Depot:
get two "Lights of American" undercabinet lights - approx $15
get one "Plant and Aquarium" bulb, one "Daylight Deluxe" bulb - approx $16
get a piece of glass cut to sit ontop of your tank and hold these lights - approx $5
for less than $40 you now have 30 watts of light for your 10 gallon.
you can disassemble the cabinet lights and build their guts into a basic wood hood as well, eliminating the need for the glass.
Let me know if this what you're looking for!
Stop by the chat this weekend, and I can help ya online if you like.
btw, i moved this topic to the
DIY forum for better exposure.
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disclaimer:
I've left out a lot of important detail in observance of brevity in the post. If you want to go with one of these options, let me know and I'll bore you with all the nity-grity details 8O
EDIT 09/23/2003
I've done some measurements using the trusty volt-meter, and the 2x59 ballast is not as ideal as a 4x32 ballast ... the current put out by the 4x32 is only a little less, and the cost savings is real good.
I had thought that the 2x59 ballast would push the whole 120 watts into a 40 watt tube, but instead it's only pushing about 80, due to the length of the bulb.
The 4x32 ballast will push 64 watts into a single tube, but difference between 64 and 80 is small, and the cost savings between getting two ballasts compared to a single ballast makes up for it... use the money saved toward additional fixtures as needed.