I have given 3 weeks and 2 weeks (Canada), we all like to think we are important and irreplaceable, but we are not

I agree that it is difficult to find a quality DBA, so the position may be vacant for a long period, but that is on the company and not on you. Reality of life

I've always given 2 weeks, though some shops have a policy of shipping you out the day you give notice with 2 weeks severance especially if you are the slightest bit disgruntled.

My contractual notice period is 3 months, in both my current and previous job(s). In my experience even 3 months goes VERY quickly when you have handover of 5 years' knowledge to a new DBA to do!

In INDIA we do have a notice period of month in general, but some times it depends on what is written in the employment aggrement one signed with an employer.

In Texas, employees are presumed to be "at will." At-will employees may be terminated for any reason. I don't realy see the point in giving a notice at all. If I find a better job with better pay, I'm outa here.

Well, I live in the 3rd word, so some things are very different.

I'm free lance DBA. I have about 10 customers. In my opinion 5 of them must have a full time DBA.

Most of that customers trust me since 2004. The last once was in 2008.

Only one of them have h/s people in their staff.

Minnesota is an "at-will" state but a 2 week notice is typical.

In the UK it is typically a month and employers hold you to it (difficult to replace the role quickly). In large companies where others share your role you go quickly. In smaller ones, they hold on to you for as long as possible.

2 weeks, though I try to be flexible. I think now I'd have to give 90 days, which is OK with me.

I usually give two weeks. I gave a month once and things got weird. Once place, as soon as I gave notice, ran me out the door.

I have never been contractually required to give more than 2 weeks, but it is not possible to impart all of the system knowledge in that time, no matter how well documented you have everything.  Unless there are serious circumstances, I will give 6 weeks if the employer already has someone who can take my place, longer if they will have to find someone.  The last time I went in search of a new job, I gave them a verbal notice that I was looking for another position 4 months before I started really looking to give them time to find a replacement.  It isn't easy finding specific skill sets that can match any company's particular needs in one person.

I've typically given two or three weeks' notice when I was an IC and four or more when I was management, just as a courtesy to the company. I never expect the company to return the favor, though...

I gave eight weeks' notice once, attached to an ultimatum for reorganization, not $$. I was hoping for, but not expecting, capitulation, but I was already well down the path interviewing for replacement entertainment when I delivered the ultimatum. Just in case the bosses weren't as honorable as I expected.

Some very interesting answers.  I've been independent for years, but in watching how employees conduct themselves through this process is very important.  I've seen a few DBA's not show the respect for their current employer and leave before a transition cycle has occured or their documentation is done.  They have done this because of the obligation that they have made to the new company they are leaving for.  Having seen what this does to their personal brand (reputation), I would strongly advise against ever "walking-out" or giving a strict one, two, or six week notice.  Sit down with your current boss, talk to them.  Explain that you are leaving and express your concern about how you leave them.  After all, they took a chance on you when they hired you; be respectful when you leave and it will come back around in your favor.  

Believe it or not, the new company you will be going to will likely appreciate the respect that you are showing your old company.  Their immediate thought will be "this guy won't leave us hanging like the last one".

I've given a 2 wk notice without issue.  In fact I was given notice that my job was ending in 3 months and left in 1 1/2 months but still gave a 2 wk notice.

Nice thought Jeremy.

I had worked in many different countries and worked with the employers, who appreciate your work and the other's who turns your Goodwill to Badwill once you resign no matter how cooperative you are.

Recently I got an offer from Big Brand but I dropped it just because the treatment they were giving was of Bonded labor not as professional (3 months notice and pay back amount of $6000).

I think 2-4 weeks should be enough as I feel my new employer won't be waiting for me for 3 months.