Not my earliest memory (I mentioned that on page 1) but I do remember quite a few things from before I could read or read well (someone else mentioned that upthread). For example, I remember riding in the car a lot (passenger seat, which was allowed then) and looking at the words on the side mirror, wondering what they said, and trying to figure it out--I realized it couldn't be something time-sensitive, like that the circus was coming to town, because they were etched on all these mirrors. Imagine my disappointment when I was finally able to read, "Objects in the mirror are closer than they appear"!
Another one is at Sunday School, we would do a lot of singing, which I really enjoyed. We had booklets with just the words to all the songs (not the music) and some of the songs were quite long, with many verses. I would be sitting there by myself, trying to just remember the words, because I couldn't actually read them from the page yet. But, I also realized that some day I would be able to, and I looked forward to that.
Also, when I was young I was completely unable to read cursive handwriting--it might as well have been hieroglyphics or some other script I wasn't familiar with. I think we learned to write in cursive in third grade (~age 9) but before that it didn't even seem like real writing to me, so I can remember staring at some things written in it with utter confusion. If someone asked me to read something written in cursive it was like they were asking me to read Martian.