We homeschooled for RE last year (after doing K-3 in our parish classes) for several reasons. My ODD has sensory processing disorder, and we live 30-45min from our church (depending on the time of day), so it was really taking a toll on her to go to school all day, be pickedup at 3:30, rushed home to use the bathroom and grab a snack, then back ino the car for a 45min drive to RE. By the time she got there she was pretty fried, and often she would melt down in class. Not good for her, the catechist, or her classmates. To be fair to her, we hadn't started OT for her yet (she hadn't been "officially" dx'd). When I spoke with our Director fo RE and explained the situation he agreed to let us HS her, since it wasn't a sacramental year for her. He said our diocese actively discourages HSing for RE but ultimately it is at the parish RE Director's discretion, and he knows us well enough to know she would actually not only be taught the things she was supposed to learn, but that she would pray with us, read the Bible, do the projects, etc.
He gave me a Teacher's Edition of the book her class was using, and I submitted her "portfolio" at the end of the year (she was already halfway through). We use the Call to Faith Series at our parish: http://www.mycatholicbookstore.com/DisplayProduct.aspx?ProductID=CU1373. For fourth grade I thought it was a little babyish, but it has a Nihil Obstat designation and I liked that it introduced Social Justice issues.
That was our first year of HS for RE, so that's all the input I can give regarding materials, other than to say that taking a friend's suggestion to get Magnifikid http://www.magnificat.com/magnifikid/index.asp for our girls has made a big difference in how they approach Mass, and it has helped them behave better at Mass too. We are going to stay with our parish's program materials, because in sacramental years they will need to rejoin their age-level in class and it will make that transition easier.
One thing I will say about HSing RE is this: it has brought me closer to my girls on a spiritual level that I had not expected. I'm finding we're praying together more often, we're discussing theology more often, and I'm getting a good refresher in catechism myself. We're all looking forward to it next year, although Brigid (my 5yo) has asked to go to class "because then I don't have to go to Mass!"