The Crafts skill is generally treated as a fluff skill simply there to allow you to round out your character and justify the fact you're playing an interior decorator or a carpenter. The only times it generally comes up is when people want to craft explosives or repair a damaged vehicle. There's more to it then that, though, if you're clever and your Storyteller is willing. You can design, build, create, and make functional things. You can also repair damaged electronic or mechanical devices. Possible specialties include carpentry, cooking, drawing, painting, pottery, architecture, sculpting, knitting, demolitions, disarming, implosions, placement, remote triggers, timers.
So what can you do with it? Well...
Sabotaging a machine (Intelligence + Crafts)
Repairing a fuse box to bring the lights back on (Intelligence + Crafts)
Rig a generator or battery charged out of appropriate goods (Intelligence + Crafts)
Designing a bomb blueprint (Intelligence + Crafts)
Building a bomb (Dexterity + Crafts)
Disarming a Bomb (Wits + Crafts to figure it out; Dexterity + Crafts to accomplish it)
Building or repairing furniture (Dexterity or Strength + Crafts)
Draw an identikit - draw a person based off someone else's description of them (Wits + Crafts)
Make fantastically fashionable clothing (Wits + Crafts)
Engineering a new design or improving on an existing one (Wits + Crafts AND Dexterity + Crafts)
Urban Planning designs that work (Wits + Crafts)
Understanding local architecture and their purposes - such as to find a secret room or determine an odd addition (Intelligence or Wits + Crafts)
Understanding what a particular tool kit is for without other guidance - such as recognising a bomb kit when you see one (Intelligence + Crafts)
Cook a sumptuous meal (Wits + Crafts)
Refine medications or other chemicals (Intelligence + Crafts)
Convince others that you're a builder, mechanic, engineer, etc. (Manipulation + Crafts)
Teach others your skill or give a speech on a crafts subject (Presence + Crafts)
Build a back up power generator for the bastion (Intelligence + Crafts)
Make a gun fully automatic when it's not meant to be (Dexterity + Crafts)
Realistic artworks - paintings, constructions of people, etc. (Wits OR Dexterity + Crafts)
Convince others of the merits of your designs or your general skill (Manipulation + Crafts)
Cover up the masquerade by explaining how technology could be designed to do that (Manipulation + Crafts)
Build prosphetics (Intelligence + Crafts)
Create fancy make-up and costumes (Wits, Intelligence, or Dexterity + Crafts)
Building a house / bastion (Varies)
Forging a weapon (Strength + Crafts)
Installing air conditioning, etc. (Intelligence + Crafts)
Repairing a car (Wits + Crafts)
Adding modifications to a car or other vehicle to make it handle better, go faster, etc. (Wits OR Dexterity + Crafts)
The reason why I place realistic pictures under Crafts than Expression is because I define Craft as what is used to produce accurate designs so if you want to paint someone how they actually look you could use craft just as you'd use craft to draw an architectural design. If you want to create a painting that expresses anything - the aristocracy inherent in the subject, a mood, anything like that - than you'd use Expression.
If you wanted to be a painter, you're better off just getting Expression but people will excellent hand-eye coordination and fine motor skills might also have Crafts because of it. Of course, World of Darkness kinda compresses a lot of skills into one so you could argue it either way. After all, a super chemist doesn't necessarily know anything about anatomy but it all rolls into Science in the end!
You can find the core article with all of the other likely links over here.