Asking for a suitable power supply for a motherboard is way too general, technically what you need is a power supply with a 24 pin motherboard connector. Really we need you CPU and GPU at the least for determining wattage. Either way, I like to recommend the Antec VP 450 as a really good basic power supply. Also make sure you ONLY buy quality power supply brands like Antec, Corsair, XFX, Seasonic, Pc Power and Cooling, Kingwin etc. Try and avoid cooler master, thermaltake, Ultra, Diablotek and pretty much anything that gives you real good prices on watts such as 980 watt power supply for 40 dollars. Bad power supplies often fry your expensive build. Also we need to know your computer case to know what kind of power supply you need.
You're missing a few specs here that'll be helpful in recommending a PSU. Primarily, we need to know what else is being powered in your system, Graphics Card(s)? CPU? etc.
When looking at PSU's there are a few considerations, brand being quite important since some brands are very reliable while some are much less so. Commonly recommended brands include Antec, Corsair, OCZ, PC Power and Cooling, SeaSonic and XFX. With any PSU you are considering, it is best to find reviews for that particuar unit from one of the following sites, HardOCP, AnandTech, JonnyGuru or HardwareSecrets. The reviewers from these sites really put the hurt on the units when testing and have the tools to check things we can't (such as ripple and noise). A PSU that passes testing from them should hold up to anything you'll throw at it.
The primary consideration, of course is the wattage (for that we need to know what you intend to power) that you will require to run. More than likely, your suggested PSU will be somewhere about twice that wattage. A few reasons for that... PSU's are most efficiant at about 50% draw, PSU's are sometimes overrated by the manufacturers (the above sites make sure we aren't victims of that) running at 50% will hopefully keep it within it's capabilities, last, the additional wattage gives some headroom for future growth - your PSU should outlast a few builds.
As far as specs for PSU's, that'll be dependant upon your needs.
List your full build - I'll give you a few suggestions and (likely) reasons for those choices