Roland CM30 Cube Monitor
As the name goes.... Cube Monitor, it is really designed as a monitor either as home recording studio monitor or live stage monitor. But, you can improvise on this one as a portable all-in-one PA system. Only 30 watt but loud enough for small venues plus it has 3 channel with one as XLR plus an AUX input where you can plug your mp3 player or iPod and use it as a backing track.
The CM30 can be linked and connect up to 8 cube monitors. Actually even just two of these that are connected together is powerful enough for a small to medium size venues. We've used this one time when we went out on a holiday and rented a caravan. We brought our karaoke and plugged it here and it sounded great. Everyone enjoyed singing. Also during birthday parties, I normally use this because it is so portable and sounds big enough on most venues.
The only downside on this one is that it does not have effects like reverb, echo or delay. So if you are a vocalist just use a mixer that has got built-in effects on it and that will solve the problem.
Overall, a very good monitor and reliable portable PA system.