Cailbri and Verdana are good substitutes for Arial.
I second the suggestion for sans serifs. Serifs are OK printed but on lit, flicker monitors they can lead to eye strain.
Times Roman or Bookman Old Style are OK.
You also need to make sure the letters are not too close together. Remember, it isn't what you find acceptable but what your audience is perceiving, even if they aren't 100% conscious of their perceptions.
A good font for section headings is Impact and most machines should have it installed.
Be certain to use softer tones in the colors as well. The dull grayish blue of the default format of this forum is an excellent example. A bright blue would be crushing on the eyes. And above all else
AVOID YELLOW!