Although many people thinks that installing Android on iPhone is tedious and very geeky, it's not anymore because Nick Dawson's BootLace has simplified the whole process. Just a few tap, you'll find iDroid installed. But in order to do this, you have to jailbreak your device. Here are the steps you can follow:
1. Run Cydia
2. Add http://repo.neonkoala.co.uk as a new Sources in Cydia
3. Install BootLace
4. Run BootLace
5. Install OpeniBoot (This apps is some kind of bootloader to choose between iOS and iDroid on boot up)
6. Install iDroid

Already tried this on my iPhone 3G and success :) Here are several pics:

In Mac OS X, you already have built-in Apache web server and you only need to activate it by going to System Preferences -> Sharing -> then check the "Web Sharing". That's it! And you already have your web server running. Just check it by typing "http://localhost" or "http://localhost/~yourusername" in your web browser.

PHP
After that, you can open Terminal and open /private/etc/apache2/httpd.conf file and uncomment this line:

LoadModule php5_module           libexec/apache2/libphp5.so

 then restart Apache service by uncheck - recheck Web Sharing in System Preferences

MySQL
1. Download package from here
2. Install everything: mysql, startup item, preference pane
3. Start MySQL in Preference Pane

Do the following to fix some stuffs:

$ cd /etc
$ sudo cp php.ini.default php.ini
$ sudo chmod 666 php.ini

In php.ini file, edit following:
1. uncomment this line and insert TimeZone:

date.timezone =Asia/Jakarta

2. find all three occurences of /var/mysql/mysql.sock and change to /tmp/mysql.sock

pdo_mysql.default_socket = /tmp/mysql.sock
mysql.default_socket = /tmp/mysql.sock
mysqli.default_socket = /tmp/mysql.sock

3. change this line from "Off" to "On"

short_open_tag = On

Restart Apache service by uncheck - recheck Web Sharing in System Preferences

In webOS world, there aren't such things like "jailbreak"-ing nor "root"-ing, you just login there and you got root access, already. What you have to do is simply following these steps:
1. go here to install Palm SDK
2. follow installation instruction according to your OS (Windows, Mac or Linux)
3. enable Dev Mode  on your Pre/ Pixi by typing this: webos20090606, turn to ON, then restart device
4. connect the device using USB cable
5. in Mac/ Linux, simply type "novaterm" in shell prompt
6. in Windows, you have to download "novaterm" exe file from here (32-bit) or here (64-bit)
7. at this point you'll have root@webos-device or something like that

You are now logged in to your webOS device and can do anything you would normaly on Linux machine. Just be careful not to destroy your device :))

Cloud Computing has been a new phenomenon recently, and while reading several articles about it, I just know that it can based on Grid or Cluster Computing. And to make it clear, here are some differences between them: