This will replace the old NPWS site www.heritagedata.ie linked to below (Nov 2007).

The National Parks & Wildlife Service (NPWS) don't make it easy. Their website with data on SPAs and SACs in ArcInfo GIS format contains dire warnings about it's total lack of "user friendliness" and you better believe them!
" .. we're sorry, but the service is aimed at specialist professional users, if you haven't the resources or don't understand the formats, then we're afraid the data must remain a closed book to you".

Download programs ..
But all is not lost. Go to the ESRI site and download the free ArcExplorer 2 viewer (12.8 MB) and the ArcExplorer v1.1 import utility (1.26 MB): OK, maybe not so simple on a dial-up line. Install them and you are now ready to do battle.

Download data ..
Download the county data you are interested in, say "sacdu.e00", the SAC areas in Co. Dublin.

Import ..
Run the import utility, the first input line (Export Filename) is the location of "sacdu.e00", eg c:\myfolder\sacdu.e00 The second line (Output Data Source) is the output folder for the imported data, which doesn't need to be created in advance, eg c:\myfolder\SACDUimport\. You should now have a series of files *.adf in folder \SACDUimport\ and also a folder called "info".

Run ArcExplorer ..
Now, run ArcExplorer. First create a project by saving the blank screen you're presented with as a project e.g. "SACDU.aep" You will see a note on the bottom right of the screen saying "No active theme": "theme" is ArcExplorer speak for what is more easily understood as a layer of data eg the SAC names, in the GIS. Shrink ArcExplorer till in occupies half your screen. Open Windows Explorer (similarly shrunk) at c:\myfolder\SACDUimport\ Highlight all the files in this folder and drag them over into the ArcExplorer window. You'll probably get a load of error messages but ignore them. Maximise ArcExplorer and click each layer's (theme) check box in the left panel.

What you get ..
You should now have the filled outlines of the SAC areas in Dublin County. The site code, name, area and co-ordinates can be read from the database by selecting say the ".pat" theme in the left panel and clicking with the information tool "i" on the SAC area. If you know the area well it is possible to fit this outline to a hard copy map or a mental map, but otherwise forget it. So this is not a lot of use without the topographic data to overlay it on. NPWS don't supply this - it is the property of the Ordnance Survey, though they both work for the same paymaster.

MicroStation ..
If you just happen to have access to Bentley's MicroStation, the weapon of choice of local authorities, you can digitise (in real metric units) the relevant county outline, lakes, etc and drag & drop the resulting .dgn file into ArcExplorer as you did above with the themes, where it will align itself perfectly. Assign a co-ordinate point beforehand in MicroStation from the Irish National Grid to the file using the key in "go=Easting,Northing" and give a corresponding data-point on screen. The Dublin maps on this site were done in this way but there are presumably better & easier ways of doing this and of using aerial photos?

How it could be done in a user friendly way. For a user friendly GIS implemented on the web using a form of ArcExplorer, though on a totally different topic, try the Government of Newfoundland & Labrador site. Click on "online map Newfoundland & Labrador" - it will be slow! Load the various layers (check boxes on the right) and read off data for the "active layer" from the underlying database. It of course has a national survey grid, topography, roads and tracks, rivers and lakes, digital terrain map, etc. If Newfoundland can do it, what is stopping NPWS?