Can I run a relay when I can't port forward?

[Puffenstuff]

Hello all,
	So, short story, I want to run an exit node, but I am on a network  
that does not provide port forwarding for incoming data. My  
understanding of network protocols has always been a little fuzzy but  
I was wondering if I connected to a proxy could I use that to make my  
relay visible to other relays.  The proxy can be transparent, all it  
has to do is route traffic to me. Then I could act as an exit node. Is  
this practical? Is any proxy I find going to be too slow to be useful?  
How would I go about finding a (free) proxy(s) (I think it would have  
to support SOCKS 4 or 5)? Does any one else do this? Is there some  
easy way that I am missing?

Thanks