Firstly, a reminder: DO NOT LOOK DIRECTLY AT THE SUN! Not with your naked eyes, and definitely not with a telescope! (Unless you're really keen on Labradors and white sticks!)
Today, just after midday, the tiny planet Mercury will pass across the face of the Sun. This doesn't happen very often: the last occasion was nearly ten years ago. The whole transit lasts around seven hours: at around 4.00pm Mercury will be just below the centre of the Sun's disc.
To look out for this great little 'astro-tick', the only safe thing to do is project an image of the Sun onto white card with a telescope (something I'd imagine most of you who read this have access to!)
Here's a couple of pictures of the simple set-up I'm using, with a 9.00am image of the Sun showing a small sunspot.
Good luck if you have a bash: watch this space for my efforts!