An interesting open-source document management system is Docear (http://www.docear.org) that blends mindmapping and referencing.

I have tried Zotero, EndNote, REfWorks and settled on Mendeley. It is not perfect but it is the closest to how I think about references, and therefore works for me.  Besides, until my thesis is completed I am not changing applications.  There are rumblings that Elsevier is considering buying Mendeley so who knows what I will use in the future. 

Use the DocEer system with DocEar4Word Plugin.  Then when you want a citation, just choose "import into BibTex" and then paste the bibtex it into DocEar.  After doing the save-all in DocEar, you will see the references available in Word 2010 under the References Tab.

Note that after you install DocEar4Word, you might have to restart your computer since you have to completely restart Word (just not close and re-open it, but do an actual close and reopen which is easier to do with a restart).

To add IEEE, etc. bibliography styles, use the CodePlex BibWord Styles package from http://bibword.codeplex.com/releases/view/15852 and install it in your Word bibliography\styles directory and restart in a similar way as above.   

After that, it's just a matter of making a new DocEar project and pasting the bibtex xml into it and then adding citations / bibliography in word.  Wish I had known about this three years back when I started my program at Athabasca instead of just learning about this now.  (I used to do citations / bibliographies manually :S )

And DocEar also lets you quickly make and modify mindmaps which might help in research brainstorming.  

- Moe