I have relatively recently been dropped into the position of being "the technical guy at the interview," and to be honest, I haven't had a lot of luck trying to come up with and use specific technical questions. What I prefer is to just try to get the candidate talking about a project and take the conversation in whichever technical direction seems fruitful.
e.g. the resumé says "implemented AJAX in ASP.NET web application to make it faster and more user-friendly", I'll ask: what sort of interactions were you AJAX'ifying? were these existing pages where you were replacing postbacks with AJAX updates or new pages? were you using ASP.NET AJAX or hand-rolling it with a different JS framework, or even no framework at all? how did you interact with the HTML coders? were you returning data and laying it out with javascript or returning HTML ready to insert into the DOM? how were you dealing with errors and timeouts?
And then of course every answer leads to more questions: usually "..and why did you make that choice?" :-)
I find a conversation like this is the best way to get a feel for whether they know their stuff or not. It also becomes, I think, fairly apparent when someone is padding their resumé by listing every project that their team or company did, even if they only had a minor involvement. If they can't converse about the project in detail, I assume they weren't deeply involved and that I should probably discount that experience and move on to something different.