Mac OS X comes with a great system monitor, and there are lots of neat alternatives as well. Our favourite is MenuMeters, thanks to its ability to provide a wealth of information from the convenience of your Mac's menu bar.
- Displays CPU, disk, memory and network statistics in your menubar
- All stats provide detailed information when clicked
- CPU can be displayed as a percentage, broken out by user and system time, or as a graph
- Disk activity is displayed through read and write symbols, and additional disk statistics can be revealed by clicking the menubar icon
- Memory usage can be displayed as a pie chart, thermometer, history graph or used/free totals
- The memory meter can display a paging indicator light
- Network activity can be shown as throughput arrows, bytes per second, and/or as a graph
- How network activity is displayed depends on user preference
- MenuMeters is an open-source app
MenuMeters is great because it can display your system statistics in the menu bar, where they are always visible, without getting in the way. Each stat — CPU, disk, memory and network — is configurable and offers multiple display methods. If the tiny little stats don't provide the information you need, you can just click on them to get a detailed view. For example, disk view offers handy information like the disk's ID (e.g. disk0s2) and CPU provides load averages. (There's more, too, of course.) Overall, you can get a pretty comprehensive look at your system via the menu bar, which is pretty impressive. MenuMeters is also free and open-source software, so if you've got the ability you can improve upon it yourself.
While MenuMeters has its graph views, they're tiny and sit in your menu bar. If you want more detailed graphs with a proper history, it just can't offer that. You're mostly limited to what's happening right now, which is generally sufficient, but if you want to look into the past as well it's not going to help you there. MenuMeters also takes up quite a bit of room in your menu bar. If you have other utilities up there, it's going to feel cramped. In some cases, apps may hide some of those menu bar apps because there won't be enough room for everything. You can make MenuMeters take up less space, but that generally comes with the sacrifice of hiding one of its displays (or at least removing certain information so a click is required to see what you want). If this is a deal breaker, check out the competition section below for some other options.
Activity Monitor, the utility that comes with Mac OS X, is a pretty solid system statistics monitor. You can see CPU, memory, network and disk activity/usage, plus it breaks down everything by task. You can (force) quit tasks as needed, investigate what they're doing, and organise them however you want. For the most part, Activity Monitor will be enough for most users so it'll do the job just fine if you don't need to constantly monitor your system activity.
iStat Nano monitors your system from the Dashboard, which is a great place to put stats if you want them easily accessible but still out of your way. You can add a single Dashboard widget and easily switch between different stats or you can add multiple versions to get a wider view all at once.
MagicanPaster is like iStat Nano but you can place the stats on your desktop like sticky notes. It seems a little obtrusive, but is probably a good option if you're working with multiple monitors.
Lifehacker's App Directory is a new and growing directory of recommendations for the best applications and tools in a number of given categories.