There's an autocomplete feature that will look at the cells right above the cell
getting the entry and try to help by matching on those few cells.
In xl2003 menus:
tools|options|Edit Tab|check Enable AutoComplete for cell values
There's an autocorrect feature (shared among all the programs in the office
suite (excel, word, powerpoint, ...).
Tools|Autocorrect options|Autocorrect tab
You can type in a unique abbreviation and excel/word/ppt/etc will convert it to
what you want.
For instance, you could have |J replaced with John.
This is the same feature that excel (and Office) uses to correct those typos:
Teh becomes The
hsa becomes has
....