If you mean freeware synths I suggest Synth1, it's free, less than 1 mb and has it's own fanbase so you can find lots of libraries for free. It's the first synth I used when I started. It's a very basic VST but doesn't sound that bad at all. Also check U-he website, they have a couple freebies wich aren't bad either. The effects listed by localspace are very good, Melda productions also offers a free bundle that's worth giving a look to.