I run eaccelerator on 5 servers I manage. You can download it at SourceForge. If I recall properly, I ran into a couple problems with it not starting properly and had to make a couple minor edits in the php.ini file.
Found an install script somewhere called "ea.txt" that only required minor edits (such as the latest eaccelerator version in the wget string and a fix for a path error).
Reviewing one of my servers, I found the old error:
[30-Sep-2006 04:04:34] PHP Warning: Unknown(): Unable to load dynamic library './eaccelerator.so' - ./eaccelerator.so: cannot open shared object file: No such file or directory in Unknown on line 0
This was caused by the php.ini file not looking in the proper path for the eaccelerator.so file. I've also found that I had to update the library when I upgraded php on a server.