After spending more time reading Webber's "Ancient-Future Time", I ran across two pieces that would be handy to use in designing worship during advent. Both of these are from the chapter on advent.
1. From the Rorate Caeli:
We have gone astray;
in the multitude of our sings we have been made unclean.
Fallen, fallen, stricken as leaves of autumn.
The storm wind carries us away,
the tempest of our evil deeds.
You have turned us from the face of your mercy,
and our iniquity has crushed us like a potter's vessel.
O Lord our God, look upon your people in their affliction; be mindful of your promises.
Send us the lamb who will set up his dominion from the rock of the wilderness to Zion, enthroned on her mountain.
There is no other whose power can break our chains and set us free.
2. From the Book of Common Prayer:Merciful God, who sent your messengers, the prophets, to preach repentance and prepare the way for our salvation: Give us grace to heed their warnings and forsake our sins, that we may greet with joy the coming of Jesus Christ our Redeemer, who lives and reigns with you and the Holy Spirit, one God, now and forever. Amen.
These could be used for calls to worship and benedictions. The liturgical tradition, while confusing to some, provides some great readings that can be used congregationally without to much explanation or confusion. I have found that using classic prayers and readings during other times, by those on the pulpit, will acclimate the congregation to the style of language, so when corporate readings are done, there is a level of familiarity.