Any apps that you've found particularly useful please.

Useful:
TVGuide – full tv listing
Now Playing – cinema times
GPS Lite – mapping and routes
iOSMaps – more mapping
Camera Genius – better iPhone camera controls (anti-shake, voice activated etc)
PhotoBuddy – camera calculator (DoF, exposure, angle of view, sunrise/sunset etc)
MultiConvert – unit conversion
Mocha VNC / RDP – connect to remote PC
Net Utility – ping / scan remote system
WiFiTrak – report all WiFi in area

Entertaining:
TVCatchup – live freeview for BBC, ITV and 4
iPlayer – streaming from BBC iPlayer
Stanza – ebook reader

Games:
(got loads but at the moment I'm playing)
PicGrid – aka nongram, griddler, Picross, Japanese Crosswords
Robocalypse – nice little real-time strategy game
DoodleJump – always useful on a sh*t break
Flags Fun – more entertaining than it sounds.

A search for the other topics which asked the same question first would have been cool. But seeing as I'm here:
Sky+
Gazette
Meters
VNC

No other apps than those mentioned above but games wise the brilliant Flight Control is still one of the games I play the most, plus GD Swarm and GeoDefense get a lot of toilet/train time.

I haven't got an ip hone, but this program has almost convinced me to get one, apart from having to draw with your thumbs :/
Autodesk Sketchbook Mobile

how about this one?

Orbital – dead simple game, but sooo addictive!

http://www.orbital-game.com/

Most of mine are just time wasters!
Pocket god (my 8 yr old loves it)
Jelly car
Monkey Ball
Flick Fishing
Harbour master
Paper Toss
Banner
etc etc

some are vaguely useful:
skype
ebay (bought pikes using solely iphone app)
ifooty
sky+
ecb cricket
sonos controller (obviously you need a sonos system)
lastfm
wunderradio
ocado (keep meaning to order my groceries while on the tube/bus but as I don't live in london and drive to work its not quite worked out like that)

Finger ninja – Its like Bopit for the iPhone, seriously addictive!

eBuddy – Instant messenger
AppGmail – Only useful if you actually HAVE a Gmail account 😉
AmazonUK
Evernote – Searchable notes made with both text or camera
MotionX GPS
UK Traffic
TubeMap
Layar
Rightmove
LastFM
Fstream
Dropbox
Bump

Weather Online (very good and has great radar screens)
Bloomberg for share prices
Bookworm
Google Earth
Ragdoll Blaster
Crazy Machine
Eurosport
TV Guide
Doodle Jump
Red Laser (very clever, point iPhone at a bar code and it will do a price search)

grinder, natch

Also:

Sky Football score centre
Sky News
Independent
Joost
Dictionary
the trainline

And for 02 customers 3month free trial of Sky Mobile tv which includes SS1, SS2, SS3, SS Xtra, ESPN, Sky news, SS News.

any bike training app's?

WeatherPro is brilliant, TuneIt iCarRadio works really well on Edge, lets me listen to 6Music, Flickr, Mobile Fotos lets you upload pics direct to Flickr, RedLaser is good for scanning book and CD barcodes and getting lots of price choices, Amazon UK, Wikipanion, CoPilot UK, Shazam, Star Walk, PacMan, Space Invaders.
[edit]iMapMyRide is good for bike training[/edit]

Best app i have used of late is logmein.

Shazam – amazing but ultimately useless
Sky+
Last.fm
Connect4 – even the lite version is unbeatable. I am 132-0 down.

Best app i have used of late is logmein.

Jamie, is it good then. I use logmein on the laptop but i would have thought that the Iphone was a bit small.

Whats it cost?

VNC or RDP (Remote Desktop) do the same thing as logmein and are free.

I use logmein on a pc and have tried it on iphone- got it to work but the screen is just too small