Without going into too much detail, I work with businesses ranging from 2 to about 50 users. This figure depends on who you count as a user, for our larger clients we (iForge - www.iforge.co.uk) manage networks with up to about 300 users.
My own areas of expertise are within infrastructure solutions based on Microsoft technologies (clients, servers, networking, email, mobility etc), but necessarily cover a wide range of areas from the basics of network infrastructure (cabling, wireless etc) to more specialist areas such as Exchange Server, SharePoint, hardware firewalls, VPNs and everything else that it takes to make these elements play together.
I have a basic understanding of programming languages, my familiarity with any particular language depends on what point of my life I needed it in! While I haven't been involved in any sort of development projects (at the code-writing level) for a while, my background generally means that I can figure out where I am reasonably quickly when dealing with projects that require an understanding of programming / database techniques.
To be continued at a later date when I have the time to talk about work rather than doing it :-)