Togu Audio Line is a free, donation based VST and AU plugin collection from the awesome Patrick Kunz. These great plugins got my attention a couple months back when some guests mentioned that they used them, and more recently I've seen that even the mighty Fred Falke is a fan.
I strongly encourage you to donate to this guy if you get some of his plugins, because they're way too much of a steal. I'll list off a few that he has up for grabs:
The TAL-U-No-62, which is based off of a Roland Juno 60, is great for polyphonic sounds. Seen above, it's a great way to get an idea of a Juno 60 without breaking your bank. There's also the TAL-Chorus-60, which is what Fred Falke used in one of his tracks. This is a great way to add the very famous vintage chorus to any synth, let alone a Juno imitator.
The TAL-Bassline is based off of the Roland SH-101, another classic synth. Off the top of my head, both guests Frankmusik and Starsmith used the real deal. This is perfect to put together a great low end, or even a lead on your track.
The TAL-NoiseMaker is another synth plugin. Not based on a retro synth, but plenty of options to mess around with too, especially if you're trying to go more "modern" and don't want the limitations of the classics.
There's even more on the site, including an EQ, a Reverb, a Vocoder, and more. This is the PERFECT place to start if you want some free plugins straight away on your new DAW (or even something like Garageband!) Part of the reason these types of plugins are so desirable is they limit you in the way the classic synths did-- that's why the programmers of the 80s were so awesome. They invented ways to get great sounds out of some synths that weren't easily programmed or didn't have a ton of options.
Check out the site here and be sure to donate if you download! I'm sure the programmer appreciates any little bit he can get for his time.