Changing sprocket sizes: will front derailleur still work? I have a hybrid, which for better or worse, I am going to use as my commuting and conditioning bike for the foreseeable future.  I am interested in changing the largest chain ring for an even larger one.  Will my current front derailleur still work? Are there other drive train issues I should be warned about?

My current setup: Gary Fisher Kaitai,  Shimano C102 front derailleur, 48/38/28 crank.  

(I would also like some advice on how large to go on this.)
According to the Shimano Tech Doc it looks like 48 teeth is the maximum recommended size and 48/38/28 is the recommended chain ring combination.

The spec sheet also indicates that the maximum jump between rings is 10 teeth, so even if you could fit a bigger ring, you would have to replace the other two as well.

I believe the Kaitai normally comes with a standard 11-32 rear cassette.  Normally 11 is the smallest number of teeth that you will find, but Shimano makes a cassette model called Capreo that you may be able to find and use that goes as small as 9 teeth if you are trying to get a "bigger" gear.  The nine speed cassette ranges from 9-26T, so you trade the bigger gear on the low end for a gear that will be much harder to pedal up hills.