Aside from your outermost pylons which always seem to be fitted with ECM pods, Sidewinders, and such, I think you can pack a LOT of Mk 82s on there. Mostly singles under the wings. Not sure about the hardpoints under the fuselage.
Here are some Desert Storm loadouts on A-10s
http://www.dstorm.eu/pages/loadout/a-10.html
"be happy in your work"

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