Time to celebrate getting your new job!! Not yet. First you need to cut cord with all your other job search activity to avoid sending the wrong message to your new employer. Plus...closing the loop the right way will also save you the headaches that will come with leaving yourself "active" on the market.
Closing the door on any aspect of your job search may not make total sense. But if you don't do this and the information falls into the hands of your new boss that you just accepted with, it will send off a red flag. Take these simple steps to clean up the trail of your job search. And, oh yeah, one more thing...if you don't feel comfortable shutting these options down because you still want to interview, then think twice about formally accepting the job! Don't be "that" guy that goes back on his word.
Remove Profile From All Job Boards
Take your resume off all the job boards. If you leave this profile up and active, it indicates to the new employer that you may still be looking. If you do want to keep it posted, that's fine. But at least make it confidential. If you do leave your profile up, just keep in mind that you will continue to solicit emails and phone calls from recruiters (this can be a royal pain in the neck if you aren't truly looking).
Deactivate With Recruiting Agencies
Send an e-mail to all the agencies assisting you to inform them that you have accepted a new position. Email is always easier then an actual phone call. Remember that recruiters are sales people. If you are a strong candidate, don't expect the agency to let you go so easily. An email may make this exchange go more smoothly. It is your choice as to whether or not you want to inform them of where you are going to work. The upside is that they'll know how to reach you (which could also be the downside depending on whether or not you liked working with them!). Also, time this discussion carefully because the second you tell a recruiter that you took a new job, this recruiter will likely contact both your new and old employer to solicit business from them...the old employer may be looking to replace you and the new employer may be doing more hiring. Recognize that this will happen and factor this into your decision to divulge any data.
Shut Down Other Interview Activity
Similarly, you'll need to email the companies you were in process with to express your appreciation for their interest in your background and to tell them that you have accepted a new job. Do this out of courtesy to them so that they aren't still keeping you in the mix. The Hiring Manager will thank you greatly for giving them the heads up and...who knows...this goodwill may come back to benefit you in the long run.
None of this may seem like a big deal to you, but put yourself in the Hiring Manager's shoes. If they just hired you and your resume is still up on Monster will seem a bit off-putting. Not taking these formal steps to clarify that you are "taken" is like forgetting your wedding ring when you go to the bar. Not cool!