UK: Now that OS have finally released some data...

...I'm thinking about getting back into my GIS saddle. Actually, I've been
thinking about it for a while, and had already identified a vehicle for my
efforts. I'm wanting to plot the locations of delegates who attend certain
networking events... just down to Postcode sectors, probably. I imagine that
some analysis of delegates will be presented to sponsors of the events, but
my initial (and main) objective is to be able to generate thematic maps to
demonstrate to delegates the concentration of other attendees. Nothing too
ground-breaking!

It's been a long time since I've done any GIS work - my last GIS work was
back in 2001 using Mapinfo and Mapguide. Apart from the fact that I no
longer have licences for either, whatever knowledge I had will have long
since evaporated.

So I'm looking for advice on to how to get started again. I've done some
searching and there are a number of free GIS tools around but I don't know
how good they are. I'm also interested in guidance on the how to convert UK
data [in the public domain] into suitable formats for these systems. No
point adopting and excellent free GIS system if I need to pay £££ to get
data converted into the right format.

Although I'm rusty as hell, I'm hoping to regain a key understanding of the
basics fairly quickly - nevertheless, I'm looking for solutions that a) have
reasonable tutorials and b) have decent community support.

Not asking for much, am I?

While my modest initial ambitions are static, in time, I might like to
tinker with an online app, that can dynamically present the data; so
although static images are my initial aim, systems with an online component
might be interesting (I'm running Windows Server 2003/IIS6).

Try not to laugh, but I do have access to a copy of MapPoint 2010; it might
actually be what I need in the short-term. That said, it's a long time since
I looked at the initial versions of MapPoint, so my snobbery might be doing
it a disservice.