A good online resource for finding out which artist or group sang a particular hit song is ClassicBands.com. It features a comprehensive list of top 40 hits from five decades as of 2015.
To find the artist for a song, you must know the song title. The pages on the site are arranged by the first letter of the song. Though the site covers all top 40 hits from 1955 through 2000, it does not include any other information, and songs that were not top hits have to be looked up elsewhere. The site also states the highest position the song achieved on the charts.