jhechanova, the best way to find great electronica songs is from vinyl/music websites and forums. How you find them is easy. You just search on google for chart listings. For example:
search for: top10 chart house progressive december 2004
If your mixing with dj equipment, and you need single tracks, then the best way to search is to search for "vinyl". Add "vinyl" into your search words. Then you can build up a serious collection of vinyl ripped single track mp3s to mash up on your cd turntables or whatever your mixing with.
If your after live recorded sets (at events) by say, your favourite dj, then you should just use software, and once you know the artist you like, search for them and place "live" in the search bar.
Its important to use the charts, if you want your electronica collection to be up to date. (tha freshest)