HI, I am working the most with the Official Dataloader but here is a link for you:Loading or Manipulating Large Amounts of Data in Salesforce.com? Here's Some Options!
Hans van Mil
Senior CRM Solution Consultant ServiceMax | Group IT
Take a look at the free Data Wizard we launched last month on AppExchange, https://appexchange.salesforce.com/listingDetail?listingId=a0N300000016cUTEAY . If you want to see/preview/correct/augment data prior to loading rather than "uploading", try http://rev.informatica.com, a low cost data prep and loading tool for SFDC and other platforms. It's free for ServiceMax employees as well.
If you are looking for things like address verification and deduping, Acme Data has a very powerful, business user friendly solution for ServiceMax that works with all ServiceMax objects, out of the box or custom. Information here: