VisionDirect.com is offering a 15% discount code - SEE15 - with the offer ending March 18th. If you're buying from the UK, be sure to read this warning. Also, if you are in the UK and looking for an insurance refund, be sure to check with VisionDirect.com that your invoice includes 17.5% tax, along with the company name, VAT number, etc.
...or even more sensible - buy your contacts from a company which fulfills all legal requirements while still giving a great price, like VisionDirect.co.uk or Lensbase.com.