Long "i"s can also come from the letter combination of i_e, igh, le, and plain old -y. Such as in the word "fry". Cool fact the word "set" has the most definitions of any other word in the English language.
The most common long a words are: ice, five, bike, mice, nice, nine, side, wide and fine. The most common short a words are: big, did, his, lip, pin, pig, sit, sip and zip (had to get a "z" in there!) Scroll down to print out some great worksheets to help you determine the differences.