You don't need your polling card to vote - if you don't have it, just turn up at the polling station and tell them your name and address. You don't need ID unless you're in Northern Ireland.
More details here:
www.aboutmyvote.co.uk/general_election_faq.aspx
If you don't know where your polling station is, check your local council's website or give them a call.
Let's try and keep this near the top so noone misses out on voting