You mentioned pagan practices, ie: Halloween, Easter, Christmas and saying bless you when someone sneezes. Could you please tell me where I can obtain a list of these pagan practices and where they came from?
I don't know of any one location that lists all or several of the practices or holidays that have come from non-Christian sources.
I will list several below. Before I do, however, I need to point out that just because they have pagan or non-Christian origins, that does not mean we should not or cannot participate in them. In many cases we have been doing them for most of our lives without realizing their origins. Even if we are aware of them, there are some we may participate in as long as we don't give them their original meaning.
Easter: Originally and properly celebrated on Passover. However, the Catholic Church set a date (and the Orthodox Church a separate date) for Easter specifically to move it away from Passover in most years (2002 being a rare exception). Easter eggs are a non-Christian symbol of rebirth and spring. (See also another questions about Easter.)
Halloween: The whole idea of ghosts and goblins, and particularly of them coming out to attack the living on a Samhain night, is in part of Druidic origin. The giving of gifts or food to appease the spirits is of Germanic pagan origin.
Wedding traditions: Throwing rice has one origin in the wish for good fortune and prosperity for the wedded couple. It may also have had the idea of driving away evil spirits by either throwing things at them or appeasing them with food. Tying cans to the vehicle is to scare away evil spirits. In Germanic countries, breaking porcelain dishes serves the same purpose. Carrying the bride across the threshold goes back to ancient Roman times, when it was to prevent the bride from being tripped by the gods of the doorway. The honeymoon comes from the Druidic Celts. All marriages were performed on Beltane (May Day), which always fell during the Honey Moon (each lunar month being given a name: honey, harvest, etc.). The married couple went into hiding and was exempt from all work and military service until the next new moon. Thus they stayed away until the end of the Honey Moon. (This was an excellent way for the couple to get to know each other better, and is similar to the Jewish military exemption for one year.)
Saying "bless you" when one sneezes goes back to the idea that evil spirits were the cause for the sneeze. Avoiding black cats goes to the idea that they were familiar spirits for witches. A fear of the number thirteen actually has a biblical background; there were thirteen at the table at the last supper and Jesus was betrayed shortly afterward.
A number of superstitions have logical reasons. It is basically unsafe to walk under a ladder. It is annoying to rock a rocking chair without someone in it. It can be dangerous or just annoying to open an umbrella indoors. Whistling backstage can be heard by the audience and so is unprofessional (although there is a more practical origin to this superstition).
There are probably hundreds of other things we do that have their origins in worship of multiple gods or belief in evil spirits. It would probably be counterproductive to list all of them, because somebody will then try to bind on other Christians that they shouldn't do them, which would go against what Paul said in Col 2:16-17: "Let no man therefore judge you in meat, or in drink, or in respect of an holyday, or of the new moon, or of the sabbath days: Which are a shadow of things to come; but the body is of Christ." We are not to judge others by whether they do or do not participate in practices that have nothing to do with salvation.