Everyone can quote the 1967 Spider-Man theme from memory and sing it ironically, but the instrumental accompaniments in that show's three-year run are some of the best and most period-perfect in animation history. Here is all of the background music, more than one hour in total.
Assembled by YouTuber 11db11 about two years ago, it was discovered recently by Retroist, who also brings you the background story of the musician behind it all. He's Ray Ellis, a longtime conductor, arranger and record producer who worked with Billie Holiday, Buddy Holly, Johnny Mathis and Lena Horne. He also composed themes for The Today Show, among other disparate credits.
Spider-Man was not Ellis' only animation gig; from 1968 to 1982, he was Filmation's composer. This part of his work was not well known at the time because Ellis and a colleague were working under pseudonyms. (For example, he was Marc Ellis, the name of his son, when doing the score for The Hardy Boys in 1969.) He died in 2008.
If you have a thing for swingin' hepcat jazz, this is your jam for the day. 11db11 arranged all of the tracks by category and timestamped them on the video's YouTube page, so you can surf around if you're looking for a particular variety. Or just put it on, put in your earbuds and zone out as you work for the day.