I just got two back-to-back installation questions via email, so let's take them in turn:
My hard drive is almost full. What can I do to Office to save space?
The questioner didn't ask about third-party applications like Monolingual or Xslimmer, so I'm not sure if those are under consideration. If you're not familiar with these apps, they remove code to applications like mine that they somehow think is unneeded. I can't state this strongly enough: do not use those applications against your Office directory. My colleague Schwieb wrote a blog post about this some time ago: leave those bits alone! in which he details the issues that those applications introduce. In short, the issue is that these unapproved applications remove code without warning, and we don't know what they're doing.
So how can you save space? Uninstall, and reinstall. When you reinstall, do a custom installation. Then you can pick what goes into your Office install. Personally, my custom installation only includes the proofing tools for English. That saves me a few MB, which probably doesn't make a difference in the grand scheme of things, but I still do it.
The biggest thing that I do myself to manage my hard drive space is to format the hard drive and reinstall the OS so that I can do a custom installation of it. At home, I don't have a printer, so simply not installing all of the printer drivers saves a surprising amount of hard drive space. There's other OS things that I don't bother to install either, but what you install is up to you. If hard drive space is a concern, I recommend doing a custom installation of everything and deciding exactly what goes on your drive. Or you can just be picky like I am. My hard drives are big enough, but I don't see the point of installing stuff that I'm never going to use.
And now, the second installation question:
Why does Office automatically put icons in my dock?
The standard installation installs everything. If you don't want the dock icons, do a custom install. The last checkbox in the installation list is to for the dock icons. Uncheck that box, and you won't get dock icons. The vast majority of people who do a standard install want to have the dock icons installed, so they're there. Getting rid of the dock icons is easy (just drag 'em out), and not putting them in the dock in the first place is also easy.
Here's an admission: I don't install the dock icons for Office. I don't install the dock icons for anything. Some people put everything in their dock. I'm on the opposite end of the spectrum: my dock is almost completely empty. The left side of my dock only has the Finder and Safari. The left side of my dock has two Office folders in it (today's dogfood version of Office 2011, and the latest shipping version of Office 2008 on the off-chance that I need it). I'm a dock minimalist, and I mostly use Spotlight to launch my apps.