The difficulty is actually finding one. From what I've seen, jobs seem to either be full time or contractual; not much middle ground.
Should I interview for a full time position and then surprise them with my intentions after I get accepted?
A better approach, if you can take the time to go through it, might be to work full-time for a year, and prove your worth many times over to the company. At that point, ask if you can move to working part-time. They'd likely rather keep a good programmer on staff part-time than let you go entirely.
In my experience, part-time programming jobs tend to pop up more frequently at research universities than at corporations. It may follow as well that a university would be more flexible in turning a full-time job into a part-time job, if asked.
You can try these for part-time work
http://jobs.smashingmagazine.com/freelance/programming
or you might find some short work in the site point marketplace http://marketplace.sitepoint.com/
You'll probably work part time ~1-3 months until they really start to pressure you to go full time (assuming they like you). This is NOT fun.
At that point you need to decide to go full time or peace out. They are not sustainable, especially when you are part of a team and the rest of the team is working full time, and they're getting all frustrated that so and so is out today because he's part time.
I would just save up and then work full time on your idea(s). Figure out your monthly expenses, figure out how many months you can go, etc. There's nothing more focusing than knowing you're losing $x a day out of your savings account by just not working - the Cortez approach, I suppose.
Caveat: This is, of course, my experience. Take it with a grain of salt.
You should learn more about basic ethics.
I agree with marrone and tjr, if you're looking for part-time right off, be upfront about it. It helps if you have specialized knowledge, or a skill that will make up for not being full time.
Sripathi
I'm dealing with this whole thing. A while back I got one company interested, blogged about it, and got expressions from interest from two other companies as well. Unfortunately I had already signed on to start a 40-hr contract so the companies, all three, said we're interested, contact us as soon as yr contract closes. I told them I have to do at least three months, they said fine. Then I get back in touch as scheduled, one company doesn't respond at all, one company goes from obsequious to condescending for no obvious reason, and the third has gone from gung-ho to tentative. So where I had three companies to choose from I now have one company which may or may not extend the offer they were previously aggressive about, and if they do, it'll be for less money.
Obviously part of the issue here is that the tech culture often assumes 50 to 60 hr work weeks in exchange for 40 hr pay. But there are plenty of organizations without that particular dysfunction and they're still not recruiting for part-time. People I work with want me to come on permanently but they don't have the ability to overcome the pointy-haired bosses on this.
Many programmers I've talked to have said they would love this kind of work arrangement. This is the weird part of it all. It's a field where competition for talent is intense, yet this is an easy way for a company to scoop other companies, and it takes a lot of work to find it.
In practical terms I've had it all my working life, just by job-hopping contracts, but it's such a tiresome way to do it, it really flakes my fucking biscuit. I've literally never once had less than two months vacation per year. It's fantastic, and if I had to deal without it, I'd deal by entering a different industry and only programming at home in my spare time. Any employer who seriously thinks they're entitled to a full year of my time for ANY amount of money is smoking such incredible crack that it boggles the mind.
Which is the other reason this is so frustrating to me. I absolutely need time for my art, my writing, my acting, my music, and my personal code projects. I am absolutely going to get that time. I get e-mail from recruiters all the freaking time. So it's going to happen either way, companies are looking to hire me, and every programmer I mention this to tells me they think this kind of arrangement would be cool to have. If it's such an allegedly competitive hiring market, you'd think companies would be like, dude, this is a no-brainer, let's scoop the other companies and pick up brainpower at below market value! But they're not. The problem is that the technology industry is managed by idiot muppets why STILL haven't figured out that programmers are not cogs in machines and do their best when rested.
So this whole part-time thing is STILL hard to swing. Which means I'm going to have to stick with the erosive job-hopping, to the detriment of my career and the missed opportunity of all these companies that say they want to hire me, because these fucking numbskull butt-trumpet ass-brained fuck-farmers are stuck in the fucking past.