If you are stuck using Microsoft Outlook to send those TPS reports at work, you've already experienced just how painfully slow it can get—but with a few quick tips you can make it usable again.
Install Service Pack 2 (or later)
While you might keep up to date on all of your Windows patches, too many people are running outdated versions of Microsoft Office (not to mention other applications). You'll want to install the very latest service pack—because Service Pack 2 has fixed a ton of performance issues for users with large mailboxes or anybody using IMAP to access their email.
The 2007 Microsoft Office Suite Service Pack 2 (SP2) [Microsoft]
Download Complete IMAP Items (Like POP Does)
When you are using IMAP to access your Gmail (or other email) account, you'll probably notice that Outlook can hang, stutter, and just generally become completely unusable—but it works just fine with POP accounts. You can make the whole experience a lot better by telling Outlook to download the entire message every time you synchronize so you won't have to wait while it slowly grabs the message off the server. Head over to the Send/Receive Groups panel by using the Ctrl+Alt+S hotkey, then drill down into your account and choose "Download complete items including attachments". The first time Outlook syncs with your mail server, it might take a little longer, but you should notice a significant improvement overall.
Force Outlook 2007 to Download Complete IMAP Items [How-To Geek]
Set up Auto-Archive to Clean Your Mailbox
Keeping a nice, clean mailbox is probably one of the most obvious, but also most overlooked aspects of speeding up your Outlook experience. You can do it yourself by setting up a separate personal folders (PST) file, and then moving old email over there on a regular basis. If you don't feel like managing the archiving process yourself, you can turn on the built-in Auto Archive feature by heading into Tools -> Options -> Other and setting up your preferences for when to archive—you may need to tweak them to fit your own emailing behavior, but the key is to keep your daily mailbox nice and small.
Configure AutoArchive In Outlook 2007 [How-To Geek]
Compact Your Personal Folders (PST) File
This is one of those tips that almost all long-time Outlook users know, but it's still important to mention. All of your email is stored in a single .PST file that grows larger and larger as time goes on, but deleting messages isn't good enough because the file never gets any smaller. You'll need to head into the Files -> Data File Management menu, then using the Settings button to take you to the dialog where you can actually compact your mailbox, shrinking the file down and potentially saving you a ton of disk space.
Quick Tip: Easily Compact Outlook Data Files [How-To Geek]
Run the Inbox Repair Tool
You've probably never thought of running the built-in Inbox Repair tool unless you absolutely have to, but if your Outlook frequently crashes and requires restarting from Task Manager, you should probably give it a run to fix all the errors you didn't even realize were there. Since your personal folders file is effectively a database, it's important to keep it clean and free of errors. You'll need to head into your Outlook installation folder, and then find the scanpst.exe file to start the repair process.
Fix Your Broken Outlook Personal Folders (PST) File [How-To Geek]
Disable Outlook's RSS Feature
If you aren't using Outlook to read your RSS feeds, you might not realize that it's still synchronized to the Internet Explorer common feed list. There's really no reason to keep this feature enabled, and you can easily disable it by heading into Tools -> Options -> Other -> Advanced and removing the checkbox from "Sync RSS Feeds to the Common Feeds List". Don't forget to delete any RSS feeds once you are done.
Make Outlook Stop Using Internet Explorer's RSS Feeds [How-To Geek]
Save Attachments (So You Can Delete the Messages)
Chances are good that the majority of used space in your mailbox is taken up by all those attachments that everybody keeps sending you. After a while, your inbox is going to get so gigantic that Outlook can't help but slow down a little, but you can easily find all of the attachments and save them somewhere else before you go through a big mail cleanup—just use the free OutlookAttachView utility to save them to a folder easily and quickly.
OutlookAttachView Lets You Save All File Attachments
Use the Mailbox Cleanup Wizard
It's not that difficult to sort a few columns in your inbox and figure out which messages are wasting the most space—but if you've got a complicated set of folders that you use to organize your email, you can quickly view all email that is older than a certain date, or too large to keep around. Head into the Tools -> Mailbox Cleanup wizard that gives you loads of options to quickly find and delete messages you really don't need to keep around anymore.
Quickly Clean Your Inbox in Outlook 2003/2007 [How-To Geek]
Disabling Plug-ins Can Seriously Speed Things Up
There are loads of great add-ins for Microsoft Outlook that add all sorts of great features, but often there are add-ins installed that are unused, unnecessary, or just pointless—and those are most likely the biggest cause of Outlook slowing down to a crawl no matter what you seem to do. You'll need to head into Tools -> Trust Center and click the Go button to edit your COM Add-ins, though Windows 7 or Vista users might have to open Outlook in administrator mode to be able to disable some of them. In my experience dealing with Outlook problems, this is the hidden one that most people never think of, but gives the biggest benefit overall.
Make Outlook Faster by Disabling Unnecessary Add-Ins [How-To Geek]
Reader Stephen writes in with an excellent, time-saving Windows 7 tip: you can create Outlook templates for boilerplate emails and pin them to the Windows taskbar for easy access.
Windows only: 
Reader David writes in with a useful tip for consolidating windows—he embeds 
Gmail has popularized archive as an easy way to keep your inbox clean without trashing email, but if you're using Outlook, archive isn't really an option—by default, at least. Here's how to add archive to Outlook.
Creating a digital certificate couldn't be easier—just type in a name and click the button, closing it out when you are done.
Next we'll create the macro by selecting Tools -> Macro -> Macros from the menu, type in a name for your macro and click the Create button.
Once you've launched the Visual Basic editor, you'll need to paste in the following macro, replacing whatever is currently there. You'll notice the 
Next we get to actually add the button to the toolbar—just right-click over the toolbars, choose Customize, and then browse down to Commands -> Macros and drag your macro onto the toolbar.
While you still have the Customize dialog open, you can rename the button or even eliminate the text, and assign a new icon. If you want to create a shortcut key for the button, you can put an ampersand (&) character before any of the letters, which will make the shortcut accessible through the Alt+<key> shortcut key combination.
Now we've got an icon to archive mail—but you'll need to restart Outlook to complete the setup.
At this point you should have a fully working solution for quickly archiving messages, but the same techniques could be used to create more advanced functionality—like a full-blown GTD system—it's just a matter of rolling up your geek sleeves and getting to work.