You can find the Phantasm plugin via the effects menu as well as via the object menu (filter)
The set is from Astute Graphics, please check out their website for trials / demos / tutorials etc
Re-color paths, shapes, images etc as well as a lot more - sort of Photoshop adjustments within the vector application
Brightness / contrast, curves, desaturate, duotone, exposure, halftone, hue / saturation, invert, levels, prepress correct, shift to color and temperature / tint
Select a rectangle and fill with a freeform gradient via the gradient panel. Go to the effect menu and select the halftone effect. You can set a DPI (lower gets larger dots or characters etc) and you can set a pattern such as 5 spoke radial etc or just use the default grid. You can also set an undercoat and a color for that. You can also go to the dot properties and change it from the default circles and go for character and click the options and set the font to use such as Arial or Myriad pro etc and also the pick random character or repeat text so you can set it to 12345 or ABC etc instead of all the capital letters. You can also use the width and height tint settings. You can create a colorful effect by using the RGB or perhaps use the sample tint etc. You can also tweak it further by using the dot gain curve to create ever more subtle or complex changes. Click OK. If you decide you want to edit it again, click on the entry in the appearance panel (window menu) and change the settings. You can also still edit the underlying colors of the freeform gradient and you will then see the letters or numbers or characters of your artwork change as well.
Halftone, Youtube video on subject
Freeform, Youtube video on subject
You can also create stunning effects using the duotone / tritone etc applied to images as well as paths etc You can set up four tints and you can use the curve to modify them even more. You can also load and save presets for this effect.