Any recommendations for a virtual breadboarding program? Preferably Software Libre.

I’ve been slowly teaching myself about electronics, and I realized last night that buying enough of all of the bits to practice with (I am a learner-by-doing) would end up being rather more expensive than I can really justify right now. Something so purely reusable as software would help a lot in nailing down the principles, leaving greater financial leeway for screwing up the bits with soldering.