I've got a pair of Specialized 74 Short Finger Cycling Gloves (sadly no longer available) and to keep them supple I rub E45 into them after every ride. If E45 is good enough for human skin the it should be good enough for leather! The rumour is that Aston Martin use E45 on their leather interiors, don't know if it's true but I use it on my BMW seats and they come up a treat!
To keep them clean-ish I just put them under the kitchen tap every now and then, let them dry naturally and treat with E45.