Zebralette -- the baby brother of the full-featured Zebra 2 -- retains the superior genetics of its sibling, packing serious punch and a large selection of useful presets, along with some deep programming possibilities and a sound all it’s own, along with some luscious built-in effects. (With names like Formanzilla and Fractalz, you know they are crazy fun.)

A longtime staple of frugal musicians, Crystal sparkles with a superior visual interface, making it a cinch to learn the essentials of FM synthesis and subtractive synthesizer programming, but delivering a widely varied set of presents to start instantly making musically-useful tones. The Mutation button morphs between presets, an effortless way to instantly cook up new sounds.

Named after a classic sci-fi movie character, U-He’s TYRELL Nexus 6 was made for a magazine giveaway, but is free for the taking, and features some seriously thick analog-like tones that will make your walls shake, and it’s got more controls and potential than some pricey commercial offerings we’ve seen. Look for “Download der Mac-Version” towards the bottom of the page.

Native Intruments Reaktor Player is a free gateway to lots of goodies, but Mikro Prism, in particular, offers an incredibly dense, lush set of presets that are a veritable candy shop of atmospheric pads and synthesized drones, sounds that are animated and simply stunning. The Reaktor Player includes other sonic goodies as well, but Mikro Prism is the clear standout.

Featuring an assortment of audio plugins, TAL offers a potent brew of totally functional instruments and truly smooth-sounding effects, some more useful than others. Particular standouts include the Elek7ro synthesizer, the Bassline bass synth, the Dub II (which can get downright bizarre) and the Reverb 2 and 3 plugins, which add some nice “air” around sounds. Grab ‘em all!

The folks at MeldaProductions offer a vast lineup of effects plugins on this page, and we particularly dig the potent MCompressor, the truly useful graphic MEqualizer, the supremely cool MAutopan (which slaps signals around the stereo field in some dizzying ways), a phaser, flanger, heck, this is a desert-island toolbox of 20(!) plug-ins that we can barely believe they’re giving away for nothing.

This longtime workhouse is a Swiss Army knife of audio effects, with up to three simultaneous effects in a chain, including compressors, reverbs, a vinyl LP noise simulator, delays, limiters and much more. The Luxonix LFX-1310 has a tiny memory and processor footprint and a deep set of utilitarian tools and effects, and is a great plugin for beginners and hobbyists.

It’s made to take drums and make them sound atomic, but the aptly-named Audio Damage Rough Rider is a versatile tool for giving that sheen of crisp, in-your-face presence to vocals, guitar and sound effects tracks, and can really make your rhythm section seem like it’s swallowed a lump of radioactive magic. Use sparingly, or go all out for sonic mayhem.