Here is Mashables Favorite iPhone Applications:

Telekinesis
- Access your Mac remotely through apps on your iPhone. Stream music
and videos from your Mac, browse your files and control iTunes
remotely. Currently available for alpha testing.

Telemoose - This one is actually useful: browse and shop Amazon.com from your iPhone. See Mashable’s fuller review of Telemoose from earlier today.

GasApp
- Another really useful one: find the cheapest gas prices in your area
by entering your zipcode. Features Google Maps integration for driving
directions, and a diesel version is available.

MoviesApp
- Enter your zipcode and a date/time to find movies in your area. Also
play the trailers (from Apple.com) and buy tickets (through IMDB).

iEventful - Find events in your area thanks to this iPhone interface built on the Eventful API.

iBrick - Three words: Tetris for iPhone.

Newsmatch
(warning:resizes browser if you’re not using the iPhone to access) - A
news quiz by Laszlo Systems: match the photo to the news item to read a
news article. Great design, but it’s a catch-22: you need to know what
the news story is about before you can read the article.

Applists
- Explore new iPhone apps…on your iPhone. How very meta. You can also
rate, share and submit apps, although there aren’t that many listed
right now.

Via

You have to use Colloquy. It works on OSX and now on iPhone. First, Download the latest version of Colloquy.

1. Download their Web-Interface plugin.
2. Install the plugin in the directory: ~/Library/Application Support/Colloquy/PlugIns
3. Create a new password that will be used to login from iPhone. Type the following command in Terminal.app with your password at the end:
   defaults write info.colloquy WebInterfacePassword <<yourpasswordhere>>
4. Open or relaunch Colloquy.
5. Visit http://yourip:6667 on your iPhone.
6. Enter the password you created earlier.

iPhone can connect to Microsoft Exchange Server with ease. Please follow the steps:-

Exchange Server Configurations

1 Outlook Web Access (OWA) must be enabled
2 Enable Exchange IMAP Support also
3 Enable RPC over HTTP for Exchange Server
4 No Digital Certificate configurations are required.

iPhone Configurations

1 - GoTo the Mail icon –> Others –> Exchange Button
2 - Enter the name and email address
3 - In the incoming server
     i) if you use OWA, enter that address (eg:- exchange.domain.com)
     ii) Otherwise, enter the  ”rpc over http” URL ( NO HTTPS)
4 - Enter the Exchange UserName and Password
5 - Enter the Incoming Server Name for SMTP
6 - leave the user and password blank for SMTP

Now Your iPhone is ready to Pull emails from Exchange Server.

1. Press the wake button
2. Slide the unlock button
3. Press the Home button if you previously were in another application, if not, skip this
4. Press the Phone icon
5. If needed, press the Contacts button. There are Favorites, Recents, and Keypad buttons as well.
6. Press the name of the contact you want to call
7. Hit their number