ok.... (all the apps I'm going to recommend don't require jail break, and are free, so pretty easily available for all)
for travel apps.
Direct.Gov Travel news
or HA Traffic
both of those are live traffic info apps that will tell you about accidents etc, un fortunately they don't really hook into any navigation software, but they are pretty good to check before you set off.
acrossair is a pretty cool bar finding/restaurant finding app.
CallRec.me - in call voice recording, so you can record important phone calls.
there's a streaming radio app called Fstream I really like
then there's the wikipedia, and sickipedia apps.
ibooks, I've also got the umms medical dictionary installed
flipbook lite is quite good (for making stick man animations)
sketchbook is very good, you can try it with sketchbook express (it's a drawing app) -you're not exactly going to be drawing complex diagrams, but if you just want to get a thought down quickly it's pretty good.
as you work in IT
Mocha VNC
Mocha RDP
Mocha telnet
Citrix Reciever
I've got a whois app as well (called free whois).
there's an app called sound level that's a fairly good DB meter
shazam is one of those what's that tune apps
I assume that you have a tesco local to you. try the tesco finder app.
not only does it tell you where tesco is (and how to get there), it also then takes the shopping list (that you write in the app) and tells you where in the shop it is, (what aisle, how many shelf units down the aisle and what shelf it's on).
the waitrose app isn't quite as cool as that, but does include recipies
there's an app called code reader, basically the premise is, you find a DVD/whatever you like in a shop, take a picture of the bar code, the app will then search online for the best deal for you.
if you like running (or cycling) then imapmyrun is a good app to have
for games
quick time wasters
Marblemash
Bored genius
geared
mine sweeper
paper toss
for a little more involved games/games that take a little more time
virtual pool (lite for free)
WSOP (World Series of Poker)
and the one that I highly recommend for games is Eliminate Pro.