Complete car amplifier for subwoofer. This is a much powerful than previous TDA1562 based version (LINK), but its based on push-pull converter so its more difficult to build. Build-in low-pass filter, all on one one-sided 75mm x 125mm dimension PCB.
Sorry, this entry is only available in Polski.
Acoustic spectrum analyzer for HD44780 LCD. This is version 2 of this device, version 1 was popular and you asked for some effects and options, so here it is :)