How do I create a circled symbol in Mathematica?

I know that Framed is used to show a frame around a symbol, how can I show a circle around a symbol?

If you don't mind having to micromanage the alignment parameters, you can overlay the empty circle character over a symbol:

TraditionalForm @ Style[
  Overlay[{x, Style[\[EmptyCircle], 24]}, Alignment -> {0.075, 0.16}]
, "DisplayFormula"
]

The exhibited font size and alignment parameters work for the font on my machine, but you may have to tweak them for good results on your screen. And tweak them again for a decent print-out. The following Manipulate can aid in that process:

Manipulate[
  TraditionalForm @ Style[
    Overlay[
      {Style[x, xSize], Style[\[EmptyCircle], circleSize]}
    , Alignment -> {xAlign, yAlign}
    ]
  , "DisplayFormula"
  ]
, {{xSize, 12}, 8, 40, 1, Appearance -> "Labeled"}
, {{circleSize, 24}, 8, 40, 1, Appearance -> "Labeled"}
, {{xAlign, 0.075}, -1, 1, Appearance -> "Labeled"}
, {{yAlign, 0.016}, -1, 1, Appearance -> "Labeled"}
]