This talk gives an overview of a linguistic investigation of individual differences in online personal diaries, or 'blogs.' There is substantial evidence of gender differences in language (Lakoff, 1975), and to a lesser extent linguistic projection of personality (Pennebaker & King, 1999). New forms of computer-mediated communication - unrestricted as to content and form guidelines - allow users total freedom for individual expression. This makes weblogs the perfect choice for exploring linguistic expression of individual differences. This talk will present findings from a study to identify linguistic features which can be used to differentiate between not only gender, but personality type. However, it is further recognised that whilst people are capable of recognising personality generally, their ability varies considerably across specific traits. In an attempt to develop automatic personality recognition, early results in machine classification by a selection of the identified linguistic features will also be discussed and compared to human performance.