The Irish Computer Society: Open to all but I would expect the onerous joining requirements (and complicated math:-)) to limit membership somewhat. It appears to lean towards academics given its emphasis on third level qualifications. You can join as an individual (well affiliate member) it will cost you €130 and for that you get subscriptions to a few magazines (ComputerScope is the only one I recognised) and a free ICS email account. They also offer a reasonable number of discounts which can add up. You get add some initials after your name (AMICS, MICS, FICS).
The Irish Internet Association: This is a business assocation for Internet businesses based in Ireland. Its focused on companies. Entry level costs are €220 and for this you get to participate in the activities of the IIA. Other benefits are loosely described on about us page but no details are supplied. You get a listing in their journal and on their members page but given this is a search page this is a dubious benefit (if I know the company name, why wouldn’t I just visit the company website directly?).
The Irish Software Association: The ISA is an employers association and is actually heavily affiliated with IBEC. They don’t post costs for joining on their website (how coy!) but the price for startups is €400. Prices do rise on the basis of the number of employees in the company. Key benefits are access to employer HR data, surveys and the like.
So if you are an individual in the IT world and would like to join a society the ICS is probably your best bet. If you sell stuff over the Internet or are an ISP then the IIA is what I would go for. If you employ people in the IT sector then the ISA is the one for you.
Copacetic 
The ISA also wind the award for the stupidest URLs.
LikeLike
Based on the ISA’s actions during the software patents thing, as far as I can tell they can be considered little more than a Microsoft astroturfing ‘front’ these days.
LikeLike