The only "global" setting that I know of is under menu>settings>display
And scroll down to "font size"
I don't know if this is only for the fonts displayed by your phone's system, or if it changes every displayed font throughout.
Give that a try
I was just poking around and also found accessibility under settings has a large text option and tried looking at a few apps including this DROID forum app and a browser and see that the text size is considerably larger!!