Asus P5B-VM SE Motherboard.
I've been using the P5B-VM from Asus for about 2-3 years now and I am really really happy with how its performed over that time period as it's been used to hell. I used to game professionally in tournements and leagues and my computer was used non stop for litterally days on end and this motherboard coped with it all.
Its currently running with my E6600 Core 2 Duo CPU which has been overclocked and it copes wonderfully. The voltages stay as they should and there is no need for tweeking. It supports dual-channel RAM and comes with an onboard soundcard which is fantastic value for money. I prefer the onboard sound in comparison to my old Creative Soundblaster Card as the onboard uses less resources and gives a better sound quality overall.
Cost wise? I paid around £100 for the P5B about 3 years ago and since then it has fallen dramatically in price. You can pick one up now for roughly £50, which I think is an absolute bargain for such a great motherboard.
Supporting upto 10 USBs, DDR2 RAM, SATA 2 and having a 5.1 surround sound card built in, you can't go wrong! Stick in a core 2 duo CPU and this motherboard will be not only reliable, but also powerful.