If you have a collection on essentialmagic.com, we have a preliminary conversion program available over the web to convert the CSV dump of your collection into a Decked Builder .coll file. You can access it over here:
For those who have an existing spreadsheet or CSV file for your collection, you can try to reformat it to look like an EssentialMagic CSV file, and then use the webpage to convert it as well. I have attached a sample CSV file to this blog posting. The important columns are "Card Name", "Cardset", "# Owned" and "# Foil Owned". We actually merge both Owned and Foil Owned into a single number.