If you're looking for the Microsoft Outlook experience without paying an arm and a leg, you should definitely consider eM Client. eM Client is a functional dead ringer for Microsoft's flagship e-mail client and organizer, with e-mail, tasks, contacts, and calendaring, and it's organized in largely the same fashion. If you know Outlook, you'll have no trouble using eM Client, though eM Client has many more features.
EM Client offers the e-mail basics: support for multiple accounts (it's less buggy with this than Outlook), junk mail filtering, and the ability to organize and search. It also fully supports Gmail as well as Facebook and Skype messaging, and it imports Outlook's entire range of data: e-mail, contacts, tasks, and calendar appointments.
One unique and very cool eM Client feature is in the sidebar to the right of the main window. It shows all your email to and from the person connected with the currently displayed e-mail or contact. This feature is absolutely worth its weight in gold, and could be mined even further by making the program contact-driven. You don't even have open the email, simply hover over it and a readable preview pops up. On the downside, I miss Outlook 2010's feature that lets create rules by right-clicking on an e-mail .
eM Client has its own hosted Exchange service so you can easily sync email between your PC, laptop, and mobile devices. At $50 per year, it's quite a bit cheaper than most hosted Exchange services. (That said, many of the more expensive hosted Exchange services grant you a free license for Outlook.) Your $50 gets you unlimited accounts and phone support. The free license for eM Client is for personal use and supports only two email accounts.
eM Client isn't perfect; I'm not in love with the overall appearance, which is just a tad busy, or the poorly divided avalanche of options in the Settings dialog. But once you have eM Client configured, you'll find its features addictive as well as inspiring.