Is an RMD required from a 401(k) if one is over 70 1/2 and still working full time and contributing to the 401(k) each week? If so, can it be done online from the 401(k) site?
No. Depositing or not, if you are still working, RMDs are not required. The following citation is from the IRS article 401(k) Resource Guide - Plan Participants - General Distribution Rules
The required beginning date is April 1 of the first year after the later of the following years:
Calendar year in which you reach age 70½.
Calendar year in which you retire.
However, a plan may require you to begin receiving distributions by April 1 of the year after you reach age 70½, even if you have not retired.
I added the last line after seeing the comment below. Thus the answer morphs to "The post 70-1/2 401(k) RMD while working, is not required by the IRS, but might be, by the plan itself. Therefore, one should check with their plan administration, or read the fine print." Keep in mind, the company running the plan makes money on volume, the 70-1/2 year old on average, would have a far higher balance than the young worker, and it's not in the company's benefit to force these withdrawals.
I am retired, and yes, the plan lets us handle the transactions on line.