Yes. Most people have company and contact information stored in various applications, so as long as you can export the contact names to Excel, you are in good shape. As part of your import, you can enter Custom Field data in the spreadsheet and bring it in to the CRM.
Once the data has been double-checked for accuracy and is formatted correctly, the Excel spreadsheet is converted to a CSV file. Do not do a mass import! Initially import just a couple of files to verify that the formatting is valid and the data has imported correctly in to the CRM.
Please note: You can mass assign ta to Contacts after import.