check this out:
http://judaism.about.com/library/3_askrabbi_o/bl_simmons_newhome.htm
"Question
What is the custom of bringing salt and bread to a new home about? Can you explain it and is there a 3rd item that is suppose to be brought?
Answer
The idea is to make a small party as means to get to know the new neighbors. The bread (and salt) is the main items in a meal - (source: "Code of Jewish Law" O.C. 177:1; 167:5). We also bring wine to a new home. Being that this party is usually done on Shabbat, we need the wine for Kiddush. Moreover, it was the way Malki Tzedek greeted Abraham - (source: Genesis 14:18; "Zohar" Leviticus 3b; "Ta'amei Minhagim" 456; "Torah Lishmo" by Ben Ish Chai, 484)."