Hi,
i've found one schema to build a hardware reset for arduino (or ethernet shield).
Here ist the link: ACQUISTA il dominio kithouse.it!
it looks great, but... i do not like that relay - it is too big for me.
Is it possible to build that using some SSR relay?
Do I have to change this schema to use SSR?
Thanks for help!
This is a quite professional circuit - each element does exactly what it is intended to do 
We amateurs are generally not so choosy..
To simplify it you can directly connect the collector of the darlington to reset, rather than through the relay coil to Vin. I can see no reason against this.
"directly connect the collector of the darlington to reset" - it souns good, thanks for help!
The reset generally has also a connection to DTR from the USB chip, or from any RS-232 connector. I presume that this connection is done through a differenciating capacitor (of around 10nF).
If not, i.e. if DTR is directly connected to RESET (which should be rare, but possible on some home brew boards), this will stress the darlington considerably