I print my covers all the time with my HP 880c printer and I think they come out awesome!
I've hope this helps ya out.
First -
Be sure that what ever cover your trying to print is the right size first, the correct size is 3240 x 2188 pixels and 10.793" x 7.293 at 300 DPI - you can resize what ever cover you may have to this size but IF the cover was sized correctly it should not alter the images appearance.
Second -
You need the right paper. To print the cover you need to use LEGAL Size paper that's the 8.5 x 14 size stuff REGULAR paper works just fine for DVD covers (with brightness of 92+) and don't be fooled into buying pre-made covers since you get 500 sheets in a package VS. 10 or 20 covers in a kit!
Third -
The best software for printing covers is Adobe Photoshop CS it's pricey but it's worth it you can also use IrfanView, DVD Cover Print or Paint Shop Pro.
Fourth -
Setttings for the final print
In your programs print settings (I use Photoshop so these are the settings for Photoshop)
Select Print with Preview from the file button
Select Page Set Up
Paper = LEGAL
Source = Automatically set
Orientation= Landscape
Click OK
THEN click Show more options
Under this new field make sure the pulldown reads OUTPUT
then click on both Corner Crop Marks and Center Crop Marks
(this will create little printed marks so you can cut the cover PERFECT)
Click OK
Then when the XP's Print pop-up appears
Select Properties
under the Paper/Quality tab
Paper Source: Automatically select
Media: Plain Paper
Quality Settings: NORMAL - Sure you can select Best but you could print 2 covers in the same time and with the same ink used!
Color: Color
Now select the Layout tab
Orientation: Landscape
Click OK
Then Click OK again and your cover will print just fine

Fifth -
To cut your cover NEVER use scissors! - Get yourself a nice smooth cutting surface that can take a beating from a razor blade
I use a piece of faux marble counter topping - I had the guys a LOWES cut me a 18x23 inch piece
I also use a metal ruler and standard one sided razor blades (the kind that comes scrappers)
Your done at this point so stuff it in your keepcase

OR you can head over to KINKOS at 3am and try to talk them into printing them on the Fiery Laser Printer!
I managed to do this twice now - at the time they charged $3 a print - I dumped $30
I've included templete sizes for DVD covers below OR if anybody needs the perfect PSD template click there -> My Template - this template even has all the markers built in!
I hope this helps!
Rikter
All keepcases use the same size cover for the front and back (1535 x 2188 pixels), the only thing that changes is the spine width.
single: 3240 x 2188 pixels (spine: 170 pixels)
:: Download Single Template
double: 3305 x 2188 pixels (spine: 235 pixels)
:: Download Double Template
triple (slim): 3384 x 2188 pixels (spine 314 pixels)
:: Download Triple Template
4/5 disc: 3508 x 2188 pixels (spine: 438 pixels)
:: Download 4/5 Disc Template
6/7 disc: 3661 x 2188 pixels (spine: 591 pixels)
:: Download 6/7 Disc Template
ThinPak single: 3150 x 2188 pixels (spine: 80 pixels)
:: Download ThinPak Single Template
ThinPak double: 3172 x 2188 pixels (spine: 122 pixels)
:: Download ThinPak Double Template
Cover/Back center marks -
full size = 1535 x 2188 pixels
Vertical quarter mark = 547 pixels
Vertical center mark = 767.5 pixels
Vertical 3 quarter mark = 1641 pixels
Horizontal center mark = 1094 pixels