In web analytics, everything is relative

What's a good bounce rate for my web site?
I get that kind of question a lot. What's a 'good' bounce rate? A 'good' time on site?
The answer, I'm afraid, is: Better than your current bounce rate. Better than your current time on site.
In web analytics, it's best to focus on your own data and on improving. Use yourself as the benchmark. This is your best strategy for two reasons:

Lack of accurate benchmarks
Accurate, internet- or industry-wide data on keyword searches, or competitors, or just about anything else, is scarce. Non-existent, really.
'Panel'-based statistics like Compete.com (which I love) and Alexa (which I'm starting to like again) sweep in an incredibly wide range of web sites. The bounce rate on your online bike shop won't compare to, say, the bounce rate on the New York Times web site.
Statistics within your own industry will include outliers at both end of the spectrum: At one end are the companies that have invested 100x your budget to become the shining pinnacle of conversion rate optimization. At the other, you'll be comparing yourself to the sites designed according to 1992 best practices. Even if you can narrow down the data in #1, it'll be inaccurate..
Keyword data from Google is about as trustworthy as a credit default swap.
Keyword data from other sources may be more trustworthy, but shows you a tiny sliver of total search traffic.

Numbers lie
Even if you could get accurate benchmarks, they still lie. Your business isn't like your competitors', no matter how similar they seem. Competitor A just fired his head of sales, so conversion rates tanked for a month. Competitor B happened to get on Channel 5 News. Her traffic tripled, lowering her conversion rate, too - but her sales skyrocketed.
Unless you've got the whole story, the numbers will lie. And you can't get the whole story.

Focus on improvement
So, if you're trying to figure out how many visitors you should be getting for 'slobber knocker', the answer is? More than you get right now.
If you're trying to figure out where your conversion rate should be? Yep. Better than what you're getting right now.That's what web analytics are for: Helping you improve. Which, as it happens, is also how you beat your competitors.