Oh there are so many! Depends a little on how skilled you are but here are a few:

House of the rising sun (The Animals) - fairly simple repeating chord progression that you can use to practice soloing

Stairway to Heaven (Led Zeppelin) - a way more complicated song of course - but the chords in the solo are a lot of fun to jam over - Am - G - F - F

Tribute (Tenacious D) - another great jam song that kind of started off as a Stairway to Heaven ripoff (try to find the earlier versions of the song and you'll see)

Oye Como Va (Santana) - This song is not in A natural minor, but A dorian minor - just replace the F (b6) in the natural minor scale with F# (6) to get A dorian.

Save Tonight (Eagle Eye Cherry)

Hit the road Jack (Ray Charles) - I think the original might be in Ab minor but most people play it in A minor when jamming.

Well, let me know how your jam sessions turn out!