Do you want High Definition / Digital programing now but don't want to pay the cable or satellite charges to see it? Do you have a standard analog TV that would normally not receive over the air broadcasts of HD? This might be the best deal you will get for awhile.
NTIA adopted regulations to implement and administer a coupon program for digital-to-analog converter boxes.
Congress created the TV Converter Box Coupon Program for households wishing to keep using their analog TV sets after February 17, 2009. The Program allows U.S. households to obtain up to two coupons, each worth $40, that can be applied toward the cost of eligible converter boxes.
If you currently have cable, satellite, or a HDTV with tuner already then this may not be for you "but" if you are like me and will undoubtedly have a few left over TV's with analog connections, or have some creative ideas on how you could use such a device (and I have quite a few 
) then this is a great opportunity.
If you decide to take advantage of the $40 offer you will want to do some research.
1) Print the list of eligible receivers because not all of the receivers sold will meet the requirements for the $40 coupon (https://www.ntiadtv.gov/cecb_list.cfm)
2) Look at the TV or device you wish to use the receiver with and make a list of the connections. RF, composite, component, etc. Also make note if you are going to use a digital stereo receiver and it's coaxial, or fiber connections. You will also have to decide if you wish to use an external antenna. Most HD tuners will use the standard amplified VHF / UHF antennas.
3) Compare the devices based on number of connections, user navigation, EPG display, outputs, etc.
4) Watch out for devices which are branded under a different name and may sell for higher prices.
5) Most important to me is that this offer is only good for 90 days from the date they mail your coupon card, and there are limited quantities with no mention of how many are left. Timing has to be right regarding price point, and requesting your coupon. The devices marketed today will be cheaper next month but will there be any coupons left 6 months from now when the new devices come to market. 
There you go. Almost free HD TV. I have a few ideas. One would be for our camping. The second idea I had was a centralized HDTV receiver with split signals all those places I don't want to pay for cable and it really is not a necessity.
Update, I just applied for 2 coupons and they will be mailed on 5/30/2008 so I have until 8/30/2008 to decide on the model(s) of converter boxes I wish to get. A quick search returned quite a few e-tailers advertising sales with coupon prices and it looks like it should be around a $20 investment for a single box which is not bad. Best Buy, Radio Shack, and other brick-n-mortar locations will also sell the same thing. Some useful links for your research.
https://www.dtv2009.gov/
http://www.dtvanswers.com
My fiends at the AVS Forums (trust them!)
WTFDA Forums (for misc. user reviews)
Comparison of convertor boxes
Leave me your comments and suggestions below. Let me know if you signed up for a coupon and what you will be using it for.