"Word Clocks" are popular projects that are not only a reasonable challenge to build, they provide a useful function as any normal clock would do. However they're open to modifications and one neat example is to program the clock with personalised messages for the end user when the clock is a gift.
Instructables member TechKiwi did just that, and took advantage of an Arduino Mega-compatible board to make addressing the muititude of LEDs simple thanks to the extra GPIO on the Mega. We really like the level of detail provided for the hardware construction along with the schematic, so with a weekend or two you can make your own version without too much effort, for example:
The most important part of any clock or timer-based project is the inclusion of an accurate real-time clock IC. Here at Freetronics we have the Maxim DS3232 real-time clock IC module:
Apart from keeping accurate time for years due to the temperature-controlled oscillator and having a tiny coin-cell for backup, it is very simple to connect to your Arduino project. A driver library allows your program to easily set or read the time and date. Perfect for clock projects, dataloggers or anything that needs to know the date and time. Furthermore it contains a digital thermometer and 236 bytes of non-volatile memory to store user settings and other data. For more information, check out the module page here.