Maize Sampler ($88) from Maizesoft allows you to publish your own sampled sound as a VST instrument.
Its many features include propagation (VSTi export) with predefined UI styles; keyswitching between 12 layers; disk-streaming; sample-mapping and Velocity layering; 16 channels with 4 stereo outputs and 32-voice polyphony; support for 8-, 16-, and 24-bit sample rates; and built-in reverb and EQ. Maize Sampler has both VSTi and standalone modes, and comes with a SoundFont to Maize Sampler format converter.
Through June 30, 2007, new purchases will receive a 25 percent discount. For more information and a free trial version of Maize Sampler, please click here.