Even after learning how to read, Reader Rabbit was a pretty good way to brush up on your words. Like most of the series on this list, there are tons of Reader Rabbit games out there - some are about filling in letters to spell words, others are more complex, and challenge (slightly!) older kids to find the right word for certain sentences.
Stick with Reader Rabbit long enough, and the games step into the muddy waters of reader comprehension - a tricky subject, even for kids that have no problem understanding words. These games were an early, useful tool for helping young children learn their ABCs.