Sadly, the Newgrounds audio portal craps out a ton of great songs that fail to get the appreciation they deserve. While there are countermeasures to that problem like the underdog list, they seem to be ineffective individually. So, I'll try to chip into the effort and keep a list of songs I think should be listened to more [apart from my own ;)].

So, I'll just add stuff with few views and reviews as I see them. As the list grows, I'll start categorizing [but not using the NG categories... they are too narrow and some aren't even genres]. Feel free to throw in your own suggestions, too.

Rock
Chrono Destiny - Chrono Trigger 1000AD remix - Forever Until Tomorrow

Trance
Krumpinkin - Love Trance
DJ Piro - Strike Down

Techno
DJ-Demolic - Universal Mysteries [damn! this guy is really good.]

House
Silent Seraph - Oh Gloria [Teaser]

Pop
xXxtEcHnOFUsIoNxXx - You Make Me Ok

Ambient
wolf-tech - The Leaving Song
VegetarianMeat - .haze.

Classical
Hawkian - Pumpkin

Breakbeats
MetamystiksInc - Angelmass [after some research, i found that MetamystiksInc is actually a legit DJ, so im kind of sad that he ditched the site and had all the songs he posted lowly rated and basically ignored. nevertheless, a cool little loop.

Hip Hop

MetamystiksInc - Warriors (feat Kal-L)