Nothing with Oracle is light weight, or straight forward.
The above error occurs whenever you don’t have the appropriate DLL’s with your project in the path. For me, my ASP.NET site worked on my local workstation because I had the ODAC installed, but not on the server. The solution is to download the large XCOPY distributable from Oracle and pull out the DLL’s you need. The oraociei11.dll is 127MB itself (yikes). Oracle may run very well, but it does nothing light weight. Checking that into my source control makes me cringe a little.
Anyway, this link helped me get started, I’ll also provide the DLL list that I used in my Bin directory: