Those who take the HSK 5 (B1-level exam) are expected to be able to read Chinese novels and news articles and be able to watch movies and TV shows in Mandarin. That being so, are there any reading or listening materials meant for native speakers that would help me prepare for the HSK 6 (B2) exam?
The HSK6 exam has a very specific, unnatural format, so studying unspecific material (such as native content), while generally helpful, will not target your HSK6 test-taking skills.
If you definitely want native material to read, I suggest (a) news articles and opinion pieces at Sina (which are simpler than e.g. CCTV) or from mobile apps such as 看点快报 or 今日头条, (b) essays (作文) written by Chinese children (e.g. RuiWen), and (c) 语文 which is how Chinese children learn Chinese (available from 电子课本网). (PS: I've been keeping an up-to-date list of resources I'm using at the Chinese.SE meta.)
However, to target HSK6 skills in particular, it would be better to follow e.g. the HSK6 Standard Course 标准教程6 (上 and 下), and taking past exams (which can be easily found via Google). However, I find that material too uninteresting to maintain concentration, so instead I'm currently taking the Coursera HSK6 course (by 北京大学) which I'm finding useful; I've finished week 7.
To improve reading and listening for the HSK6, the general advice is to systematically learn the vocabulary:
...people are prepping for the HSK, my advice is always that the single most important thing to do is learn that vocabulary ...
John Pasden, You Can Learn Chinese (~56:30)
The Chinese HSK YouTube channel contains many useful videos about the HSK. In particular the listening 听力 video describes how the HSK6 test deliberately contains words outside the HSK vocabulary, and explains how to deal with them (also relevant for reading).
For the HSK6 exam, the listening section has crystal clear standard Mandarin without accents or slurring (generally both male and female voices); they won't um and ah (or 那个那个……) or otherwise misspeak; it will be mainly emotionless, and there won't be visual clues; etc. This is unlike movies, TV series, etc.
Edit: Some YouTube channels I'm finding particularly useful while studying HSK6: 大鹏说中文-Speak Chinese With Da Peng for HSK6-level listening practice; Carly LetsSpeakXYZ reads out example sentences for the HSK6 (among other content); Mandarin Corner also reads out HSK6 example sentences; ChineseEddieG汉语艾迪 reads out the HSK6 Standard Course textbook content. I also find 黃瑽寧醫師健康講堂 useful; he's a Taiwanese doctor who has some "Muggles courses" on medical topics (intended for native speakers).
You'll see this repeated everywhere: reading speed is critical to success on the HSK6 exam (and even the HSK5 to some extent).
When reading and understanding, reading speed is very important. Thus, an appropriate reading speed for the HSK6 is around 160 characters per minute.
Coursera HSK6 course, week 3, lesson 1
Hacking Chinese estimates that at less than 130 characters per minute, you simply won't be able to read the whole text. So no matter what you're reading, if you're improving your reading speed, it will meaningfully help. (It's also noteworthy that this is a long exam, so you'll need to read efficiently despite being tired.)
I've repeatedly seen the advice do not read everything on the HSK6 exam, which is a main theme of the Coursera HSK6 course, week 3. In particular, they emphasize understanding the strict format, focusing on the parts which are important to read, and skipping ahead to the questions. You'll even encounter advice to flat-out guess on questions 51 through 60 (语病) and save time for other sections: ...for us muggles, the best strategy will be to simply GUESS IT. My strategy here, again, is b-b-b-b-b-b-b-b-b-b. (11 Steps that Helped Me Prepare and Pass HSK 6); see also Are HSK6 questions 51 through 60 (语病) so difficult that it's reasonable to just guess? at Chinese.SE.
The Coursea HSK6 course highlights topics which repeatedly occur on the HSK6 test (using past exam questions as examples), and thus are worth paying more attention to:
- Week 3, lesson 1: Chinese real historical stories (and Chinese dynasties); generally no foreign history. (In the video it tells the story behind the saying 千里送鹅毛.)
- Week 3, lesson 2: fables, stories with some moral, etc. (In the video it's letting go of physical possessions, which were previously useful but are now a burden.)
- Week 3, lesson 3: introducing a famous building, etc. (In the video it's 悬空寺 = "Suspended Temple".)
- Week 3, lesson 4: objects of some Chinese significance. (In the video it's 砚台 = inkstone.)
- Week 3, lesson 5: animals and plants. (In the video it's 向日葵 = sunflowers.)
The week 7 is about science, technology and finance:
- Week 7, lesson 1: discusses scientific research into "venting" (倾诉) to friends indicates it is not meaningfully helpful.
- Week 7, lesson 2: discusses "the alertness point" (警戒点), where you may be fast asleep but are awoken by certain stimuli.
- Week 7, lesson 3: discusses "electronic paper" (电子纸).
- Week 7, lesson 4: discusses "solar wind" (太阳风).
- Week 7, lesson 5: discusses "financial checkups" (理财体检).
(This is where I'm up to at the time of writing.)
Reading and Listening Resources for HSK 6 (C2)?
Those who take the HSK 5 (C1-level exam) are expected to be able to read Chinese novels and news articles and be able to watch movies and TV shows in Mandarin.
I feel obligated to highlight how HSK6 is not even close to the C2 level; see Wikipedia for a more realistic comparison (see also How long does it take to be fluent in Mandarin?): HSK6 is either late-B2 or early-C1 (although it doesn't assess speaking Chinese). That being said, people who intend to use Chinese (and not just pass the HSK6) don't exclusively study HSK6 material.
There are articles like HSK 6 gets you halfway which measure how useful HSK6 is in some way. To get a more realistic idea, when I was late-HSK5 level I posted on Reddit about how I transcribed and annotated an entire article about the celebrity 金星 (金星大儿子更像金星！19岁的他为金星庆生，网友：这个儿子没白养):
This is a relatively simple news (or celebrity gossip) article. These were the words I was unfamiliar with at the time:
HSK6 (10): 家喻户晓, 编织, 感慨, 潜移默化, 靠拢, 特意, 罕见, 争议, 认可, 任命
non-HSK (26): 互动, 高调, 秀恩爱, 露背, 吸睛, 遮阳, 另类, 复古, 挽, 般配, 献上, 收养, 亲生, 长相, 挑, 血浓于水, 血缘关系, 饱受, 诋毁, 抨击, 这阵子, 实属, 现任, 轨迹, 找茬, 回怼
non-CC-CEDICT (6): 白养, 同框照, 味十足, 油纸伞, 信命, 热映
The take-home message is: even after HSK6, we're going to need to keep looking things up in the dictionary (and 6 of these words are not even in the CC-CEDICT dictionary), but it's possible to get a fairly good understanding of simple articles at around HSK5.