I'm a little familiar with linear disassembly with something like Olly, but am wondering if there is free software that does tree disassembly other than the free version of IDA. I've searched but haven't found anything so far.

You could try the OllyGraph plugin by Joe Stewart or the modified version called OllyFlow by silverfox (henryouly). I think they both require the GPL wingraph32.exe, which came compiled with the older versions of IDA. I think I tried one of them long ago but totally forget the results.

Both are available at OpenRCE, if not the CRCETL

http://www.openrce.org/downloads/details/173/OllyGraph
http://www.openrce.org/downloads/details/178/OllyFlow
http://www.hex-rays.com/idapro/freefiles/wingraph32_src.zip

I was wondering if someone could of made a plugin for Olly but didn't find either of those, thanks!