V-USB with ATtiny2313 to communicate with Android
What you want to do is going to be very difficult for two reasons:


The ATtiny2313 does not have any usb hardware whatsoever.
Most (all?) android phones are only made to be USB slave not host


I would recommend getting a bluetooth solution which you can talk to over some simple serial interface on your ATtiny2313. That will then talk to the bluetooth on your android phone which is designed to be a host.

For the bluetooth solution for the microprocessor side I recommend something like this, and on the Android phone you can download the app called "Blueterm" which is essentially a terminal that when you type a message and then press enter it sends the message over bluetooth. It also detects the bluetooth slave device (the chip from sparkfun) and connects to it.

EDIT: Ok some brief googling tells me I'm wrong about all Androids only being USB slave. It seems some more recent phones coupled with more recent OSes can in fact be USB host. However, it doesn't change my opinion that the bluetooth route would be much simpler.

On VUSB - that is a complex-ish code library that I will not delve into, any questions about that are probably better suited for StackOverflow. The hardware however is not that complicated, USB uses differential signaling for its data lines. Everything you need to know about pull-up and line terminating resistors can be found on this guy's site. You also need to make sure you have the right voltage level for an android's usb port.