Worship: I love those passages in Isaiah and in Revelation where we see the angels in deep adoration of God and of the Lamb.I could probably come up with more.. I think that their purposes are very similar to ours. It seems that God has chosen them, and us, to bring his kingdom to earth. He could do it alone but for some reason He has chosen to include His creation to facilitate His will.
Communication: Scripture is replete angelic visitations bringing messages from heaven to earth.
Ministry: In Hebrews they are called ministering spirits. It brings up the images of angels ministering to Elijah and to Jesus.
Protection: I love the term guardian angel and how the most innocent and vulnerable amongst us have an angel watching over them.
Gotta wonder what life after death will look like.. maybe we are more like angels than we think :)