There aren't many decent free maintenance utilities around for OS X. Most of them you have to pay for apart from something like MainMenu, which I've started using.
However, iTool bucks the trend as an easy-to-use, effective, and free maintenance utility that aims to keep your Mac in tip-top condition. iTool is ideal for the first-time Mac user who wants to perform Windows-style maintenance tasks on OS X but doesn't know where to start. You can even automate tasks so you don't need to be around to use it.
In terms of ease of use, iTool is probably the simplest maintenance tool on Mac I've ever used. Everything that you want to administer or maintain is listed down the left-hand side. So, if you want to clean your browsers, just select 'Internet'. Or, if you want to restore Spotlight's indexing, just click on 'Restore' and then click and unclick the options you need.
You can also automate tasks to work while you're away such as a monthly script repair or to periodically clean your Internet cache. There's also a checkbox to shut down your Mac when all these tasks are done and the ability to force clean the trash (and show what's in it at the same time) which I always like to see in these kinds of apps.
iTool will not satisfy power users but for newbies on the Mac, or those wanting to perform the most basic of maintenance tasks, iTool is all you need.