I second the recommendation of Eric Bogle's song "And the Band Played Waltzing Matilda" - it's a very powerful song and since it is about Gallipoli and Suvla Bay.. I think you'd find it most interesting.

If you have the old Irish Rover's LP, Tales To Warm Your MInd.. give a listen to the song 'The Village of Brambleshire Wood' about a village that's lost a generation of young men to the Great War. It's not available on CD. I always found that one to be a great statement on the futility of War.

I'm sure if you search the Mudcat on WWI, you will turn up many threads with lots of songs.