Before Looking at the shoes you want to decide what pedals you want to get first then get shoes to match.
The pedals are first sorted into 2 clasifications 1) Road and 2) Mountian
For doing a triathlon I would think that a road pedal would be best but I am not that sure
The road pedals come iin four basic models
1) SPD (by Shimano) which uses a cleat shaped somewhat like a arrow
2) LOOK which has a large triangle shaped cleat
3) Speedplay which is a small disc shaped pedal
4) Time
5) There some 3rd party manufactures which are almost always compatible with either the LOOK or the SPD and are much more inexpensive
The Look are probably the most comfortable and the SPD the eaisest to get out of and about 75% of all shoes are compatible with both formats
Once you know the pedal you are going to use you can then select the shoe to go along with the pedal
http://www.performancebike.com and
http://www.nashbar.com
are 2 good places to start looking. The both are solid companies and have a good amount of pictures to see the merchandise