I bought a new Nike Dri-Fit Singlet the other day and have run in it twice.  First, I should note that I am a heavy sweater and we are experiencing a heat wave at the moment with extremely high humidity.  Nevertheless, this singlet holds a remarkable amount of sweat.  At the end of both runs, I took it off and wrung it out which resulted in more water than you would get from a soaked washcloth after a shower.  If you don't sweat, then I'm sure this singlet would work just fine.  If you do, then don't buy this singlet expecting it to stay any drier than a cotton under-shirt.

This is how Nike describes the singlet:

NIKE Dri-Fit Mesh Singlet – Men’s  MSRP $25.00

Overview:

Say goodbye to the sweat factory with this venting top. The Nike Men's Dri-FIT Mesh Running Singlet features our elite Dri-FIT mesh technology for supremely breathable, ultra-sweat-wicking performance. Self-fabric binding at the neck and armholes and a straight bottom hem deliver comfort and fit.

 Swoosh design trademark heat transfer at left chest.

Fabric: Dri-FIT 100% polyester knit mesh.

Technology:

Dri-FIT

This high-performance microfiber polyester fabric actually pulls sweat away from the body and transports it to the fabric surface - where it evaporates and leaves the skin cool and dry. It's all you need for hot days, and a critical base layer for cold days. Stay dry. Stay comfortable. No matter what.