CPU: Core i3 2125 / 2105
MB: Gigabyte GA-H67N-USB3
MEM: 8GB - 2x4GB 1600MHz CL9
SSD: SATA 3! Crucial m4 128GB? (Often recommended series) Samsung seems also recommended some times.
HDD: 2,5" 5400rpm for storage / Time Machine (5400rpm more silent then 7200 but slower)
CASE: It is hard to find a good case. Look at mini-itx.com online store but their is a lot more out there. The PSU takes up a lot of space but most low power consumption system can easy work with Pico PSU 150/160W. Search for "Apple Cube 2.0" here in the forum.
Graphics: Integrated in Intels processors isn't for gaming but can handle low graphics. Look at reviews. The case also depends on if you want an graphics card. And if you plan for a extra graphics card, get a case with support for DTX board (ITX with extra card slot, like Silverstone SG06.)
I just got a Silverstone SG06 "special" with USB 3 ports at front. I will rebuild it some, remove PSU, change it for Pico PSU, vibration damp hard drive bay, sound isolation and other stuff to make the case better.
I have 8GB ram in my current system and I do not do much and still some times it writes to the swap.