Hi! I found this image in one of the topics (Keep sharp edges when using subdivision surface) I was wondering how can I make this theme! Thanks!
You can make a theme from the Themes tab of the User Preferences (from the File menu).
From the "Presets" drop-down, pick a base theme, and then just start tweaking! You can see the results immediately, and when you're done, you can hit the plus button next to the Presets box to save your theme.
On Mac, you can find your saved themes in
~/Library/Application Support/Blender/<version>/scripts/presets/interface_theme (hit Shift+Ctrl+G, paste it in, and put in the correct version).
(On Linux, it's probably somewhere in ~/.config, and I've got no clue where it is on Windows. If someone does know, please edit my answer!)
The theme in your picture actually looks like the Graph theme, which should be installed by default. You should be able to just select it. (But be sure to hit Save User Settings at the bottom! Otherwise you'll lose your changes when you quit.)
Edit: Fonts are not part of the theme at all. You can change your font in the System tab, by entering a path to a font file in the Interface Font box in the bottom right (of course you can just use the open panel button).