I learned about the R4 card and RomUlation .net from the uncle of a child's friend. What I didn't get was where do I get the card from?
You can get an original R4 from www.shoptemp.com They are trustworthy, very reliable, and ship for free. If you can afford another $6 or $7, I recommend getting an Acekard2i though. This is also the cheapest choice if you have a DSi, as an original R4 will not work on any DSi.
If you get the r4 change the firmware to wood r4 for better compatibilty than the official firmware for it. It can play most games execpt probably the odd one or two.