Encysted small redworms (cyathostomes) I suspect that due to the odd climate we have been experiencing over the winter with above average ambient temperatures this condition is increasing. We have had cases both before and after Christmas which is a little unusual as they are supposed to occur in the early spring. Prevention is best using either a 5 day course of Panacur (Panacur Equine Guard) or a single dose of Equest. (Do not give to animals under 6months of age) If you haven't used either of these products since mid Nov2011 please dose your horse/pony.
Hoof abcesses. Again due to the wet weathger the hoofd is waterlogged and soft allowing bacteria to work up the white line and cause abcesses. Allowing the hoof time to dry out will limit the risk. Hoof disinfectants will help as will regular farriery.
Mud Fever. A similar story to the hoof abcesses. Skin that is continually wet will be more prone to bacterial disease. Try to dry the legs overnight in the stable and brush off excess mud. Skin barrier creams are helpful but far from 100% effective.