A glimpse of angels

The Hebrew word for Angel is mala'ak. See here a list of angel appearances in the Old Testament.

The Catholic Encyclopedia entry on "Angels" builds on the Hebraic Tradition and the New Testament, and adds input from Church Fathers. On the question of evil angels:

The distinction of good and bad angels constantly appears in the Bible, but it is instructive to note that there is no sign of any dualism or conflict between two equal principles, one good and the other evil. The conflict depicted is rather that waged on earth between the Kingdom of God and the Kingdom of the Evil One, but the latter's inferiority is always supposed. The existence, then, of this inferior, and thereforecreated, spirit, has to be explained.

There are also multiple traditions regarding the ranks of angels. Here from the same entry:

We know on the authority of Scripture that there are nine orders of angels, viz., Angels, Archangels, Virtues, Powers, Principalities, Dominations, Throne, Cherubim and Seraphim. That there are Angels and Archangels nearly every page of the Bible tell us, and the books of the Prophets talk of Cherubim and Seraphim. St. Paul, too, writing to the Ephesians enumerates four orders when he says: 'above all Principality, and Power, and Virtue, and Domination'; and again, writing to the Colossians he says: 'whether Thrones, or Dominations, or Principalities, or Powers'. If we now join these two lists together we have five Orders, and adding Angels and Archangels, Cherubim and Seraphim, we find nine Orders of Angels.

The angelogical lore in the Hebrew tradition is vast -- see for an idea of its scope, this site from the Jewish Encyclopedia. It also has a table of the chief angels and their responsibilities.

Another look at angels is found at Bible.org, which seems to be of Protestant provenance. The site cites Psalm 148 in support of the fact that the angels were created:

1 Praise ye the LORD.

Praise ye the LORD from the heavens:

praise him in the heights.

2 Praise ye him, all his angels:

praise ye him, all his hosts.

3 Praise ye him, sun and moon:

praise him, all ye stars of light.

4 Praise him, ye heavens of heavens,

and ye waters that be above the heavens.

5 Let them praise the name of the LORD:

for he commanded, and they were created.

Of course Wikipedia also has a wide-ranging entry on Angels.