I have definitely heard of numerous children who learned to read in a very advanced manner after doing the 100 days lessons. I know the book is fairly cheap and there are numerous copies in our library system. Personally, I didn't like it, but it's a cheap investment and would resell very well.
My DD taught herself to read on her own, but we are huge bibliophiles here and read to her 1-2 hours a day her entire life and we have a pretty huge in home library so there are always books around. But I think that the Leap Frog DVDs actually really helped her to put it all together, while we weren't even paying attention. She surprised us by reading one day, we had no idea she could do it.
Anyway, here's a link:
http://www.leapfrog.com/Primary/Pres...ndergarten.jsp
Chances are, you can borrow the DVDs from your library and see how your child reacts to them.
I agree that Starfall.com is a really good site for the children. I think Studydog rescinded their free program but both my children LOVED it when it was free. I would suggest checking your 7 year old's eyesight with a real optometrist to make sure that your DC can really see the letters well. Both of my children could actually read and I had no idea that they had extremely poor vision until we got real vision exams at an optometrist. Supposedly children can squint and change the shape of their eyes to help them see better but it's not so good for them to do that. (even if you don't see them squinting) I can't help but wonder if your 7 y.o. could have a vision issue that might make it harder and more tiring to try to read.
Good luck!