We have used some of the Kumon workbooks at home. it is a drill and kill thing but surprisingly, my kids haven't minded doing them. We only do one page a day though. It has helped ALOT with math facts.
I like Kumon. We used one of their workbooks to teach DS how to tell time. True, it's very drill and kill, but also logical and clear.
I wasn't sure how to proceed with telling time... I never taught DS's older sister. She could just tell time, and before her class covered it, so I'm not sure where she learned it. (Does it sound bad that I don't know? LOL) DS didn't pick it up as easily, and the Kumon book made teaching it to him very simple.
