The following is a list of the soul gems in addition to which creatures will fit in them (creatures will fit into higher quality soul gems as well if you don't have the correct type). All but grand soul gems can be bought and found on random creatures throughout the world. Note that not all variants of creatures are included in the below table as are those with no soul value. Also note that, unlike Daggerfall, the souls in the soul gem can never be released.
For souls in the expansion packs, please see Tribunal:Souls and Bloodmoon:Souls.