Ixl didn't do it for him... When he's really frustrated with math facts we set them up as algebra problems (7x=21) and that somehow makes it more fun for him.
IXL has fact practice just like that; here's a sample:
http://www.ixl.com/math/grade-3/solve-for-the-variable-multiplication-divisionThere are also some less drill-y practice resources out there in print, like
this. Math facts are used in all the problems, but they're all different. I remember that the "math for the gifted" workbook series had some fun problems too. I'd also check out the other usual suspects: Life of Fred, Ed Zaccaro's Primary Grade Challenge Math, Murderous Maths, Perfectly Perilous Math, Mathematics Enhancement Programme, Sunshine Math, etc.