Uncle Jimbo's Get Mediaeval
|"Downward and onward!"|
Skill Challenge: Research a Ritual
6 successes for a heroic tier ritual, 8 for a paragon tier ritual or 10 for an epic ritual seems reasonable.
Only characters with the Ritual Caster feat may make checks towards the challenge.
Obviously Arcana or Religion, but I think that's almost too obvious. I'd allow only a total of 2 successes from the key skill of the ritual, and say that either Arcana (for Arcana rituals) or Religion (for all other rituals) must be the last success in the challenge. Making this last check requires a payment of half the market price of the ritual. Whichever of these skills is not the key skill for the ritual can contribute 1 success.
If the ritual has a different key skill than Arcana or Religion, allow up to 2 successes from that skill, but the last success in the challenge must be in Religion.
Streetwise to locate people who might know about the ritual or similar magical effects. A success in Streetwise contributes no successes but allows a character to make a Bluff check for 1 success, Intimidate for 1 success or Diplomacy checks for any number of successes up to 1 less than the total. If a character fails any Bluff or Diplomacy check, an Insight or Thievery check immediately afterwards gains a success but does not negate the failure.
Dungeoneering to find out about strange magical effects and rare components: up to 3 successes. Nature can be used in the same way but only for 2 successes.
History to find out about past uses of the ritual or similar effects. Any number of successes up to 2 less than the total.
Once the characters have gained at least 1 success (or successfully used Streetwise), pay half the market price of the ritual to gain 1 automatic success, or the full market price if that success will end the challenge.
You might want to look at Ars Magica for further ideas about magical research.