The T recently spent lots of money on website "renovation" and it does look outstanding. But structurally the thing is full of shoddy HTML. I'm still trying to find a page that validates. Not that my markup is always perfect, but for the money, there's no reason to be using font tags or to serve malformed documents. Plus there is nary an RSS feed to be found!
Anyway, wheresthet.com is not affiliated with the MBTA in any way. It's simply an application I wrote that pulls data from the service alert pages and stores them in a database. The above mentioned bad markup sometimes leads to weird data anomalies, but overall it works really well.
You'll notice it has a barest of bare designs. This is intentional, as I'm intending it to be browsed from mobile devices. It looks great on my LG CU500v and it will probably look even better on your shiny new iPhone (but if you can afford one, why are you riding the T?). Of course you can view it in your desktop browser or subscribe to one of the RSS feeds. You can also have the updates from the main feed emailed to you.
I should also note that the timestamps on the alerts are not the time the message gets posted to mbta.com. Instead it's the time my application acquires the information. It pulls every 20 minutes, so it should be close.
I plan to add to this when I get some time. Meanwhile, let me know what you think.