I sing in a local community choir (mid-Cheshire) and we do include some folk/traditional songs in our concerts. They are usually arranged for SATB with a few SAB.

Our musical director is keen to have a really good mix of items in our concerts so we can be singing Schubert, Mozart, Sting and Early One Morning all in the same programme. It works!

The 'folksongs' we sing:

Danny Boy
David of the White Rock (my favourite)
Early One Morning
The Lark in the Clear Air
The Last Rose of Summer
O Waly, Waly
Hamba Lulu (Zulu traditional)
I'm Going up a Yonder (Spiritual - does this count?)
Swing low, sweet chariot (another Spiritual - they are new to us this year)
When the Saints Go Marching In (the music says it's trad. arr. Hood)

We do seem to be including more and more trad. stuff (as well as quite a bit of 'pop' which I, personally, am not keen on) presumably because the audiences like it!

Apropos of nothing, one of the songs we sing regularly is Amanda McBroom's 'The Rose'. After a recent concert an audience member was heard to say 'The Rose is just about my favourite folk song'. What???!!!
Personally, I can't stand it as it's too sickly and sentimental for me but that's just my own, very biased opinion so don't shoot me down in flames 'Rose' lovers, will you?