A lot of times, we all have needs to have multiples calendars, keeping stuff from home and work seperated and being able to access those informations from everywhere. Here is my configuration using just one Google account, hoping it will help those who want to achieve the same thing.
First, what I need:
Just one email, where I can get personnal and work related emails. At least two calendars, one for work, one for personnal stuff. A single contact list and a way to sync everything and my notes between my iPhone, iPad and computers over-the-air...
Setting up the Google account:
Using any browser, at least in desktop mode, go to your Google account on the internet. In the email configuration, add labels as much as you need like "work", "family", "friends", etc... While managing your labels, make sure that each of them is IMAP enabled by selecting the checkbox at the far right. Once all your labels are done, go into the filter management screen. Create filters that will associate a specific label for your imcoming mails. For example, anything that comes from @google.com coul be lableled "Friends". Those filters can trigger on keywords, senders, subject... Once all your filters are created (generally 5-10 are enough), you are done for your emails...
Now the calendars configuration... Go into the Agenda, and at the left, you can add new calendars and configure them to meet your needs. For example, the default one is your name. Another one can be called "Work". When creating new calendars, you also have the options to share them with other people. Can be useful to share your schedule with all your colleagues. Once everything is done, go to that link to enable synching for all your calendars with IMAP: http://www.google.com/calendar/iphoneselect . Save and your done!
For contacts, it's pretty much the default configuration, nothing to do here...
So now, your Google account is setup properly and ready to work with your iDevices...
On the iPad/iPhone/iPod:
In General-Emails, calendars and contacts, create a Google account. Enter your credentials, and only activate "Calendar" and "Notes". Then create another account, but this time select "Exchange". Enter your credentials, using m.google.com as the server. No need to enter a domain name. On this account, only enable "Emails" and Contacts.
Back in the emails accounts configuration, scroll down to setup your desired parameters as how long to keep calendars items and other stuff. In the Contacts section, make sure that your "Exchange" account is selected as the default. In the "Push" configuration, make sure to enable notifications for new emails for the "Exchange account"
You should now be setup!
What it does?
When a new email comes in, you should be notified at (almost) the same time on all your devices (if push notification was enabled). Even if the "Google" configuration let's you retrieve your emails, it does not support push notifications so you have to rely on automatic fectching each 15 min at the fastest... This is where the "Exchange" configuration does shine, letting your get your emails as they arrive.
Open your Mail app, and at the top left, you can click to see all your folders. You'll see the inbox, spam, etc... And all your labels will show up as folders at the same time. This is pretty neat since you won't have to move your emails into folders to keep them organised. The filters previously setup will take care of organizing them for you. Just click on the folder/label, and all that was labeled by that name will show up. Labels and filters can do wonders to keep your emails organized. Basically everything is kept in the inbox, and labels are used as views, easily configurable to meet your needs over time...
Now your calendars... Open the calendar app, and at the top left, you can click on that button to show only one calendar or all of them. Pretty useful! The only cons is that when using the Google account instead of the Exchange, you won't be able to "Invite" contacts to an event. But the Exchange account does not support multiple calendars from Google. At least, I did not found out how to do it. But I prefer having multiple views since I can still use the browser to invite contacts in my events... When adding a new event, remember to select the desired calendar because it will end up in your default calendar.
Then open your Contact app, you should now see all your contacts from your Google account. Make that you have selected the Google (Exchange) account as the default otherwise your new entries will be stored on your device locally and not in the cloud.
Remember we enabled "Notes" while setting up the Google account previously? Open your Notes app, and add a new note. The note will be saved in your emails under the label "Notes". It is actually an email sent to you, from you. But your notes will be synched between all your iDevices in the Notes app, and available under the label "Notes" using the browser on a computer or in Safari.
So using only one Google email address, you can be organized to handle personal and work related stuff whitout duplications or loosing data. All of this can be done without a computer and iTunes.
... That was a long post ...