Otherwise known as procrastination when I should be typing up edits on my essay!
(Apologies for difference in image sizes - I have pasted them in piecemeal, and cannot be bothered to figure out the resizing possibilities!)
The tri bra top is basically a sports bra made out of material suitable for immersion in water, and notionally styled so that it could be worn on its own (not by me, I do not have the figure or the temperament to run in one of these on its own, I will wear a shirt on top! - but it is in theory part of the design mandate for many of these tops).
If you were on a very tight budget, you could certainly use a regular sports bra instead of a tri-specific one (I have even worn a sports bra and tri shorts now and again at Chelsea Piers when doing a swim-spin combo & having forgotten the tri-specific top); some racers will have a full-length sleeveless tri top either over one of these or instead of it, but I prefer a short-sleeved real bike jersey for my ride so I usually wear tri top and shorts for the swim (alone or under wetsuit depending on temperatures - maybe a throwaway cover-up t-shirt if I am going to be hanging around a long time pre-race and don't want to be half-nekkid), then don the bike jersey in transition. I've also seen fast women racing the "stroke and stride"/aquathlon-type race wearing one of these under a regular women's bathing suit so as to have additional support on the run.
The tri top I have used for a long time is a Tyr one much like this. It's my fourth season of triathlon, strange to say (this was my race report for the first triathlon I ever did, the Florida 70.3 three years ago in May 2008!), and I've worn this top a lot in training as well as racing; it never was as good as a real sports bra for longer-distance runs, and it became increasingly floppy with age, plus seams that once were relatively chafe-free started to give me more trouble.
Since triathlon is a gleefully expensive hobby, and since a long-course IM-branded race is one of the best ways imaginable to rationalize leaching large numbers of dollars from the bank account, I thought this would be a good time to upgrade...
I picked two different ones to buy based on some digging around online.
The first one was the Pearl Izumi women's elite crop (in pink and gray, or "flamingo and shadow grey" as they would have it).
Zoot women's tri bra top (I think that's the model I got, but am not 100% sure - color "Caribbean" as pictured, i.e. turquoise and yellow).
(This is the bike jersey I will wear - since I train in one like this, using a sleeveless top would be a recipe for disastrous sunburn - and I'll change into my 'cerise' Patagonia Draft t-shirt for the run. This amazingly lightweight and comfortable shirt is in a suitably lurid and celebratory color scheme - when I was running in the park yesterday, a baby girl sitting on her mother's lap on a park bench noticeably coveted it, and reached her hands out to me each time I went past them!)