(click on photos to see a larger version of the track)
Both masked shrews and northern short-tailed shrews have 5 toes in the front and back. They have claws, but the claws don't always show up on their tracks.
Their front tracks are about .25-.5 inches wide and long. Their back tracks are .25-.5 inches wide also, but are usually about 1 inch long. Masked shrew tracks will be slightly smaller than short-tailed shrews.
Both kinds of shrews have several different walking patterns, and usually show tail markings of some sort in the middle of them. Their tracks are most easily found in the snow. You're more likely to see the trails they leave as they forage than their tracks.
Least weasels have 5 toes on both feet, but their smallest toe might not show up, so you may only see 4 toes. They have claws, but the claws don't always show up on their tracks. Their front tracks are about .5 inches wide and .4 inches long. Their back feet are about the same.
You will often find their tracks in a succession of small groupings.
Long-tailed weasels have 5 toes on their front and back feet, though the fifth toe does not always show up. They also have claws that may not appear on the track. Their front and back feet are 1.9 cm long and about the same width (the width might be just a little bit bigger).
Long-tailed weasels move mostly by bounding. As a result their tracks are almost always found in individual groups of all four feet. They usually land with their back feet in front, so the tracks that you will see in front are actually the back feet. Their groupings of tracks are usually between 50 to 130 cm apart because weasels are very good jumpers.
Mole footprints are rarely seen. Moles have five toes on the front feet and five toes on the back feet. They have large claws that help them dig. Their tracks are most likely less then 1 inch all around, but their claws may make the track look longer at times.
What you will find more often than a track is a long trail of ground that has been pushed up a bit where moles have dug below it. These trails are a reliable way to track and identify moles.