A is for (whoever gets Z starts the next theme)

[twyngwyn]

Grows on a tree

A is for Almond

[twyngwyn]

X is for Xenophobia (Greek)

[countessalmirena]

Y is for yam (West African)

[twyngwyn]

Zodiac (Greek)

next theme: Look down, what do you see?

A is for Ankles

[countessalmirena]

B is for bag

[twyngwyn]

C is for Carpet

[countessalmirena]

D is for doggie doo-doo

[twyngwyn]

E is for Earth

[countessalmirena]

F is for fingernail cuttings 

[twyngwyn]

G is for Grass

[countessalmirena]

H is for hoi polloi (metaphorically and in a disgusting sense)