Software
Freeware can be great, and has really become better with time, but is still and will always be a few years behind pay software. In addition finding quality freeware requires trying a lot of bad freeware before you find quality freeware. With my suggestions for a home user usually the differences between pay and freeware software is miniscule.
A few work well for a buisness as well, but if using freeware for buisness you should remember that freeware doesn't offer paid support, so finding solutions when it doesn't work will take more time and patience which can effect your buisness more then the cost of paid software.
Office
OpenOffice for a home user will do everything Microsoft Office does. It even opens Microsoft Office documents. It does have the occasional conversion problem and is missing some rather advanced functions, but as a home user this beats paying for Microsoft Office for options you will likely never use. So uninstall that Microsoft trial that came with your computer and install OpenOffice for free.
The one thing that doesn't come in the OpenOffice suite is an equivalent to Microsoft Outlook. If you need an e-mail client then install Thunderbird. Also freeware this will do everything Microsoft Outlook would do for a home user. Personally however, I prefer to just use a hosted web solution like gmail since this saves you from backing up your e-mail.
For creating diagrams I suggest Dia. This is another freeware product that is great for flowcharts, and even electrical diagrams (as you can see in my mechatronic projects). You can also try the OpenOffice Draw that comes with the OpenOffice suite, but personally I prefer Dia.
For creating PDF's PDFCreator is a great freeware software. It creates a printer named PDFCreator that you print to from ANY program, and it creates a PDF. No need to make sure it's compatable with your software. If your software can print, then you can PDF it.
Security
A home user should get at least the minimum level of protection. That's why they should at least install AVG Free (free for personal use) for the basic protection windows missed in their security center updates, which included firewall, and malware protection (once you install windows defender), but no virus protection.
Sync/Backup
There are many syncronization programs out there, and I've tried all I could find in my search for something that does everything I want. My favorite is Windows Live Mesh. It's easy to setup, automatic without being a large burden on your resources. You can share/sync folders with other users. And my favorite is you can sync with 5Gb of free online storage. This way the computers you're syncing with don't even have to be on at the same time and this makes a good off-site backup solution. Some added benifits include being able to take over your system, and managing/downloading your files from your online storage both via your mesh logon.
Some may have an issue with MS having your files stored on their server. This is a personal choice you'll have to make.
There biggest disadvantage is you can't sync to network drives. However, if your network drive is on a windows machine you can install Windows Live Mesh on it and then share from it. In addition once this product came out of beta, they stopped supporting XP.
If you need to sync to a network drive that isn't a windows machine, or the desktop of an XP machine, or don't like programs that rely on MS servers you can use Sync Toy. It's just as easy to setup, but is not automatic (you can however setup a schedualed task to run it when idle).
If you're a medium sized buisness, then you likely have the resources for something more scalable like redirect.
CD Burning Software
CDBurnerXP is a freeware CD and DVD burning program with an interface similar to easy to use Nero. What can be so great about that for a buisness? You can create a familiar interface that is the same accross your whole company rather then having a differant interface depending on what software came with your CD burner.
Try it before messing up your computer
If you find software that you want to try, or you want to start messing around more with windows, and you don't want to cause harm to your system download Microsoft Virtual PC. This allows you to simply create a "Virtual PC" that runs on your computer. Then you can do whatever you want to your "guest" or virtual system, without damaging or infecting your "host" system. In addition you can configure it so that if you mess something up on your virtual computer you can just close it and it essentially forgets everything since you started the virtual pc.
Alternatively there is VMWare server. I have tried their new 2.0 and found it to be a resource hog, and an akward interface (especially for someone using it for a virtual machine or two, rather then a big server infrastructure). However, VMWare Server 1.0.10 is great. In addition to what Microsoft Virtual PC does VMWare Server 1.0.10 can run Linux OS's, and emulate a 64-bit OS (on both a 64 and 32-bit host OS).
In addition to convert a physical machine into a virtual one you can download Disk2vhd or VMWare Convert. Great for backing up a computer before a reformat. Who ever heard of a backup you can bootup before this?