You can use MS Paint to print them (and DVD covers for that matter). You just have to make sure that the settings are correct:
Open the image in MS Paint
Go to File: Page Setup
Select legal-sized paper
Select landscape orientation
Set all margins to zero (Paint will reset them to the printer's minimum)
Select "OK"
And of course, make sure that you max out the image quality in your printer settings.
This works every time if the resolution of the jpg file is set to 300 dpi (which all covers here should be). I have had some covers that I downloaded (don't remember which site) where the number of pixels was correct (e.g., 2175x3240), but the resolution was set incorrectly. You can deal with this in one of two ways. If you have image editing software, you can simply change the resolution setting (making sure that the total number of pixels remains unaltered). In Paint, you can simply scale the print in the "Page Setup" dialog. For example, 96 is 32% of 300, so if your image is set to 96 dpi, you can set the scaling to 32% and it will print fine (I have actually done this, and there is no loss of quality or size distortion).
I'm not sure if you will actually need legal-sized paper for blu-ray covers. It depends on how close to the edge your printer can print.
As for cases, I bought some blu-ray cases from US Plastic, and I was happy with them. Some of the cases were broken on arrival due to inadequate packaging, and I emailed photos of the damaged cases to US Plastic. They sent replacements right away with lots of extra packaging. These cases have the locking tab that can be folded out of the way if you don't want to use it. Link is
here. The trick is optimizing shipping cost. When I bought these cases, I added like three of them to my cart and then calculated shipping. Then I added one case and re-calculated shipping. I kept doing that until I found the best shipping price compared with order price. I think I ended up ordering eight cases because the shipping for 7 was more than for 8, and the shipping for 9 was also more than for 8.
Others have pointed out
this site for blu-ray multi-cases, but I have not ordered from them.