I just started loading slugs this year. So far I have not had too much success. I'm still learning though. A couple of links that sell reloading supplies:
http://www.slugsrus.com/They sell hammerhead slugs. They are a full bore slug. These same slugs are sold as the Hastings Laser Accurate. I get excellent results with them out of my USH. Make sure to order their roll crimping tool. The metal roll crimpers from some other places won't let you complete a roll crimp on full bore slugs.
http://www.precisionreloading.com/They sell various reloading supplies. Including new and used hulls.
http://www.ballisticproducts.com/They aslo have quite a bit of reloading tools and components. They have developed sabots that can be reloaded. There are a lot of guys try to work out bugs on these but they show potential.
http://www.lightfieldslugs.com/lightfield/They sell Lightfield commander slugs which are another full bore slug. I have shot a couple dozen of these as well with about the same results as the SPW Hammerhead slugs. Still a work in progress...
http://gardnerscache.com/index.htmlThey sell complete Lyman sabot kits except the powder. It's a one man operation there, he fills quota for the week fairly quickly, so if you decide to try them, keep an eye on his website Monday mornings. He will turn off the shopping cart after he has enough orders for the week.
Most slugs can be roll crimped. I use a drill press with the Precision reloading roll crimp tool to finish the shells. I have a Lee Load-All II to star crimp the Lyman slugs. You will need a good powder scale. I would highly suggest purchasing the Lyman Shotshell Reloaders Handbook. You are also going to need some powder. When you order different slugs, they will come with different load recipes for different hulls and powders. Follow these recipes until you find the right combination that works in your gun.