Fun song to play. I think the most famous version of this song was done by the
Weavers (Pete Seeger's old band). Here's a pretty basic flatpicking arrangement. Enjoy!

   G (320003@1)                       C (x32010@1)              
E|----3---3-------3-----3--|----0---0-------0-----0--|
B|-0--0---0-1--0--0-----0--|----1---1-------1-----1--|
G|----0---0-------0--2-----|-0--0---0-2--0--0-----0--|
D|-------------------------|-------------------2-----|
A|-------------------------|-------------------------|
E|-------------------------|-------------------------|

   G (320003@1)            D7 (xx0212@1)E|----3---3----3--3--------|----2---2-2-----2---2-2--|
B|----0---0----0--0-0/1--0-|----1---1-1-----1---1-1--|
G|----0---0-0--0--0--------|-2--2---2-2-----2---2-2--|
D|-0-----------------------|-------------0-----------|
A|---------------------------------------------------|
E|---------------------------------------------------|

   G (320003@1)                      C (x32010@1)             
E|----3---3-------3-----3--|----0---0-------0-----0--|
B|-0--0---0-1--0--0-----0--|----1---1-------1-----1--|
G|----0---0-------0--2-----|-0--0---0-2--0--0-----0--|
D|-------------------------|-------------------2-----|
A|-------------------------|-------------------------|
E|-------------------------|-------------------------|

   G (320003@1)           D7 (xx0212@1)             GE|----3---3-3-3--2--2-2-2--2-2--|--------------| (320003@1)B|----0---0-0-0--1--1-0-0--1-1--|--------------|
G|----0---0-0-0--2--2-2-2--2-2--|-0...---------|
D|-0-------------0--------------|--------------|
A|------------------------------|--------------|
E|------------------------------|--------------|