Where can I find those symbols on Mac OS such as Apple logo, small iPhone?
You need the Special Characters Palette. You can usually access it from almost any program and it's a generic palette, so the changes you make, will be global and shared across applications.
It's almost always (by convention) located in the Edit menu of any application. In this case, this is Google Chrome's Edit menu:
Once you select the Special Characters palette, you will be presented with the following palette, where you have to click on it's "toolbar" and select Customize List:
From the sheet list, scroll down until you find Sign/Standard Symbols, and/or experiment with others. You can find things like: ☎☏✆��
Please bear in mind that:
1) The above screenshots were taken under OS X Lion (10.7), the Snow Leopard version of the Character palette is similar and you will find it in the same place, but as far as I can remember, won't allow customization, you'll have to play seek and find. :)
2) OS X Lion supports Emoji, which cannot be displayed in Stack Exchange and I'm not sure what other OSses support them natively. This is what the Emoji look like:
Open Keyboard from System Prefs & klick show Keyboard & Character Viewer in Menu bar Open language & text in SystemPrefs & select Input Sources, & check keyboard & Character Viewer.
Then go to the menu bar, click on the inout sources icon & choose character viewer.
There is also a Dashboard widget from Tacowidgets called CharacterPal that will display all of the extra characters in a small window. place your mouse over the character, and it will display the key combination to create the character.