- Ireland to get declarations from the other 26 member states which will satisfy a sufficient number of 'No' voters, then repeat the referendum (which as they point out is the easiest option for everyone except the Irish government, and therefore won't happen)
- Start negotiating again from scratch (which they then go on to rather confusingly combine with an EU-wide referendum to ratify the outcome)
- Keep the current Nice Treaty in place, with minimal changes (which they seem to think could include the EU foreign service)
- A two-speed Europe with those who want to go for deeper integration forming a core (but who are they?)
Myself, I think that it is important to distinguish between two different "what next?" questions. I see the logic of proceeding with the ratification process elsewhere - if nothing else, it will reveal what other flaws there are in the Lisbon Treaty as currently on the table. The constitutional court cases pending in Germany and the Czech Republic may be as crucial in this as the Irish referendum.
The immediate "what next?" is how to proceed with the institutional appointments after 2009, when the current arrangements for the European Commission expire and when Croatia is due to finish its membership negotiations, with a view to joining in early 2011. It's pretty clear that the loss of the Irish Commissioner was indeed a factor in the 'No' vote, so I imagine that that, plus perhaps some fairly minimal re-jigging of the voting weights, may be factored into the Croatian accession treaty (since accession treaties do not require referenda). The permanent President of the Council and the new-look EU foreign minister are both now impossible to see happening as soon as next year. (In other words, I agree with option 3 as put forward by Bertelsmann.)
The less immediate "what next" is to ask what people actually want from the EU, rather than what the EU wants its people to vote for (in other words, I also agree with Bertelsmann's option 2, except that they do not go far enough). I nailed my colours to the mast here two years ago, proposing that a consultative assembly be convened with a certain amount of jury-type random selection of EU citizens, to decide (in paraphrase of Douglas Adams) what the question actually is. (I explain a bit more here and here.) Of course there's no guarantee that even the outcome of such a process would be able to gain popular support at referendum; but perhaps the outcome would be of a nature that did not need to go through such a process. One can never tell.