Some simple pixel art GUI elements:

• Frame (ridge) with gray background
• Inset (at the same time button frame) black
• Default, active and disabled buttons in red, green and blue
• 4 Icons for Buttons: Up/Down Arrows, CW/CCW Arrows
• Letters A-Z, Number 0-9 for use on the default gray background
• Screw heads

The update to version 0.3 added several more items:

• Default, active and disabled buttons in gray
• 5 new Icons for Buttons: Left/Right Arrows, +/-, X
• A gray "button" that can be used as scroll bar
• Letters A-Z, Number 0-9 for use on red, green and blue background
• Additional font style for disabled elements

Preview image is at 2x scale.
Frame and inset are sliced up for use as 9-patch.
Buttons can easily be sliced up in the same way.
Drawn with DawnBringer's famous 32 color palette.
They are programmer art quality level, I guess.
Everything comes as tidy GIMP files.

I would highly appreciate if you let me know where you are using these, but you don't need to.
Also, if you use them, credit (link to this page, for example) is appreciated, but not required.