Resisting a Spell

When a spell is cast upon someone, specifically the sort that has a contested roll by the target, does the target (if its a mage or some other supe) feel something special beyond anything like an Unseen Sense or Mage Sense might feel? If someone casts Telepathy on another Mage, but the mage resists... does the target feel his mind being probed at all?

I think no, given that you need a Mind spell active to sense mental powers at work.  You would have your Unseen Senses go off and that's it.  Of course, if you start scrutinizing yourself, you can pick up the presence of an active spell with any Arcanum.  You can even identify it as a Mind spell if you get enough successes on the scrutiny.

There's 3 things to consider here:
1) Any time a non-concealed supernatural power happens near a mage, he 'feels' it. Nothing more specific, just 'magic just happened'.
2) If he has mage sight on, he can generally see magic flying around, especially if it's the arcanum covering that sort of power
3) If you know mind magic you get the power to more easily detect when someone's messing with your noggin

Apart from those, no. you don't automatically know that someone's casting a spell on you just because you're rolling a resistance roll.