Today I want to round up some useful links regarding Mandarin pronunciation.
One article that I came across fairly early on in my learning process, but wasn't able to make use of until later, is the Sinosplice article on Mandarin pronunciation. The details of the discussion are perhaps a bit too advanced for a beginner, but reading it now as someone who has spent some time listening to fluent Mandarin speakers, I find it very useful in explaining some of the things that seemed inconsistent at first.
For pronunciation of specific words/characters, Forvo is worth a look. It's a crowdsourced collection of pronunciations of various words in different languages, and it has reasonable coverage of Mandarin. The thing I like about it is that it collects a number of different people's pronunciations of each word, and also tells you roughly where in the world each person is from. Make sure that you listen to the Mandarin (listed as "Chinese") pronunciation of the word, not the Cantonese, Hakka, etc.
Another option is the Our Chinese reading tool (thanks to sunflower for the link). This is for individual characters only; although it lets you enter words, it doesn't take tone sandhi into account, which can be misleading. The MandarinTools entries that I link to from my character posts also fail to take tone sandhi into account, but are useful for individual characters. However, YellowBridge, which I also link to, does seem to make sure to incorporate tone sandhi into its pronuniciations.
One point to remember is that different people have different accents in Mandarin, just as they do in English. I've noticed that the presenters on the cookery programme 天天飲食 have what I believe is a Beijing accent, with lots of retroflex "rrrr"ing at the ends of words, and a completely different pronunciation of words such as 黑 (hēi/black) in comparison to other sources (example video on YouTube, around 0:48 and again around 1:10 and 1:30 and several times after that). Here's a blog post I found on the subject, if you're interested.