I have never built a cabinet before, but I found a plan for kitchen cabinets on one of my favorite blogs, www.ana-white.com, here (thanks, Ana!). I modified the plans slightly to fit my space, removed the upper horizontal panel and made the cabinet doors taller for more storage space.
You can see that I started with melamine panels for the sides and bottom, but while it is nice and white, the edges can show wear, and it is not paintable. Melamine is also fairly heavy. I decided to switch to plywood panels instead, so that I could paint them the same color as our bedroom walls, which is a slightly off-white color, to give it a more professional built-in look.
Here is the wood version, after I added the doors. I used a good-quality sanded plywood sheet, cut into pieces for the sides and bottom (I added the top later). The doors are made from laminate pine wood (pieces of wood basically glued together into a panel), with pine moulding as their frame. I later painted it, but it would also look very nice stained.
This might not look like much, but it was an important step for me in learning how to build the rest of the unit. It was the building block that the remaining project was modeled after.