Almost every resume I see contains some sort of summary or profile at the top. Is that really needed and, if so, what should it include?
I prefer the word summary because I think that if you include one, that's what it should be - a summary of your experience and other key qualifications. I don't tend to use the word profile because it implies a subjective description of your character traits, and I don't believe that serves any purpose. Everyone thinks they are motivated, hard working, and a born leader with excellent communication skills, but the fact is no one really cares what you think of you, they want to know what others think of you.
Summaries are useful when you've had a lengthy work history and the reader truly could benefit from a snapshot or 'at a glance' section. For example, if your resume is at least two pages and you've held at least a few different jobs in the last dozen years, you may want to summarize that experience for the reader at the top of the first page. For example:
12 years' experience as a top-ranked district manager with Gap, Old Navy, and American Eagle. Managed up to 10 stores at a time with $90M in sales and 600+ employees, including the highest volume Gap district in the western region and the 2nd highest volume Old Navy district in the east.
However, if your resume is one page, or perhaps two, and you've only held one or two different positions in the last 12-15 years, a summary may not be necessary since it's much easier to calculate total years of experience and find key information such as sales volume, district size, etc.
Another reason you may want to leave out a summary is space. If your resume is two full pages and you don't want to go to three (and there may be good reasons for that), and you feel everything included on those two pages is really valuable, you may want to leave out a summary and perhaps use your cover letter for that purpose.
Lastly, consider using a tagline instead of a full summary - basically, one line under your name that contains the key facts. It saves space, avoids repetition, and attracts attention. For example:
12 years' experience as a top district manager
with Gap, Old Navy, and American Eagle