Can I use custom ethernet shield with standard libraries? I would like to make a custom ethernet card that uses the enc28j60 like this:
DIY Ethernet card

but first I would like to know if I can use the standard libraries which can be used with the ethernet card which is in the market like this:
ENC28J60 ethernet module
The libraries don't care whether or not you're using a shield, only that you're using a device they support and that you've wired it up how they expect (or that you've modified the library to use the actual wiring you're using). So find a library that supports the ENC28J60 and knock yourself out.