Agents and Novellas and Poems

I know of some who rep novellas and short stories. Not so sure about poetry... check AgentQuery.

http://www.querytracker.net/

A database of agents, what material they accept and lots of other useful info.

Also see:

http://www.agentquery.com/
http://www.publishersmarketplace.com/

It isn't generally worth an agent's time to rep poetry.
Same for novellas as there are few markets that pay significant money for them. Where you do see novellas being repped it is because the agent already reps the author's longer works.