what is this common sports song?

Are you thinking of this?

http://www.youtube.com/watch?v=ZKyEyxwqS2c

It's "Mony Mony" by Tommy James & the Shondells.

Here's Billy Idol's version which is the version usually heard at games.

http://www.youtube.com/watch?v=IAmgTNATJkk

If you are indeed thinking of the song Fungo linked to, it's called 'Rock and Roll' and was first performed by Gary Glitter in 1972.

It actually has two parts- the first part (Side A when it was released) has vocals. Side B (commonly refered to as 'the Hey Song') is the instrumental part, and charted at No. 7 in the US. It was Glitter's ONLY Top 10 hit in the US, and he only had one other song even break the Top 40 in the US.

However, he was a huge success in the UK (which is where he's from).

You're probably thinking of the "Hey Song!"

http://www.youtube.com/watch?v=F5NSi_phshw