I'm already accustomed to building my own PCs, already have built around 5-6 systems. However I haven't yet built a server. I want a LAN server for my home to store all my digital photos and probably have it running a RAID 5 array.
What are some of the differences between a server and a normal PC I should be on the lookout when buying parts from http://newegg.com ?
For a home server like that, any current desktop PC will do the job. You'll probably want to make sure that the motherboard has a gigabit LAN port, a controller that handles RAID 5, and enough SATA ports on that RAID controller to make RAID 5 worthwhile.
The above posters are right. Most of what makes a server tick is the software running on it. I have a home Apache webserver and the only thing different about it from being a regular PC is the webserver software running on it 24/7.
There is specialized server hardware, but for a home server, you probably won't be needing that much performance.