I have an iphone, but I think at least the first 2 below are available for BB and Android.
Evernote:
remote storage and indexing of notes etc. that I make on the phone or computer. Here's what's coolest:Let's say I paint something on a jobsite. I snap a picture of the paint can--it's tagged by location so I can see notes/pics from a given jobsite later. Also, the pic is sent to a remote server which also does OCR (text recognition) on anything it can. So a month later, I can look up, let's say "Moore" and see the picture of the Benjamin Moore paint can.
If you snap pics of signs, even t-shirts, you can look 'em up without having to manually enter keywords or anything. It even works on business cards--I type "Shondra", for example, and I immediately get my pic of her AT&T business card. Useful free version, much better paid version.
Reqall:
I press a button and say "dinner with Melanie on thursday at 7 pm" and a few minutes later the appointment's been added to my calendar and I get reminders however long before the appt. that I specify. Also location aware, it reminds me if I'm near Menards that I said I needed lightbulbs from there. Really cool. Useful free, cheap and better paid version.
Craigspro:
gives you better access to Craigslist than the site itself. You see photos without having to click through to the posting. Plus much more.
Lastly, every smartphone should grab a calculator that does fractions for us Yanks (on of only two countries in the world that hasn't switched to metric, I believe). I use Fractulator.