For VST effects I recommend the Kjaerhus Classic series - separate delay, reverb, chorus, phaser, flanger, compresser, limiter and eq - and they're all free. The SIR_1008 Reverb is not to be missed either. It's a free convolution reverb that sounds every bit as good as a commercial product.
For VSTi's, start with Triangle II, Synth One, and Free Alpha. Then add Superwave 8, Karma Killer and Texture and you've got most of the synth bases covered for free.
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