I could be wrong, but I have a vague memory of a thread about this somewhere where there is a 10 speed cassette that goes from 11-34 - I think i remember Debw & Luna cycles commenting on it, it was about a cyclocross bike and I think they were also talking about whether you could use 10 speed shifters for 9 speed cassettes in the back as well.

It does require all new shifters, but:
You actually might be better off going to a 9 speed and putting a 11-34 mountain biking cassette in the back instead of changing to a triple...

If you don't want to get new shifters...
If you get a smaller bcd compact crankset, you could get a compact crankset with 46 & 30 tooth chainrings or something like that... But I don't know that's going to help you anymore than the triple.
http://blogs.phred.org/blogs/alex_we.../01/22/95.aspx