Bumpers
Having the conductive traces touch your table is not so great, you can protect your Arduino by adding bumpers to the bottom
You can buy these from McMaster Carr part no. 95495K66 (in large quantities) or your local hardware store.
Free up some RAM
If you're working on a project that needs a lot of memory, you can free up 100 more bytes (10% of the RAM on an ATmega168!) by lessening the serial receive buffer. By default its 128 bytes, which is quite a bit!
Open up hardware/cores/arduino (or cores/arduino) directory, and edit the file named wiring_serial.c or HardwareSerial.cpp
Near the top is a #define RX_BUFFER_SIZE 128, which means 128 bytes are used for the buffer. You can change this to 32 (or even 16!). If you have almost no serial input, make it as low as you'd like as long as its > 0.
You can also save another 2 bytes by changing rx_buffer_head and rx_buffer_tail from int to uint8_t
