1. Referrals. 

Make sure everyone in your company, your peers in other companies, your friends, your relations and even your hairdresser know you are recruiting and what you're looking for.  You never know where the next recruit will come from.

2. Your website

Every website should have a jobs board - even if it's just a blog where you list the titles and job descriptions.  And while you're there.. why not tell the candidates what a great place to work this is?

3. Reed.co.uk

They've just started charging, but there are number of free listing spots in a year.  From personal experience  - worth doing.

4. http://www.ctp.org.uk/ctp/employers

Places people coming out of the armed forces.  Free to advertise and a source of well trained, effective team members at all levels.

5. Newspapers

Not in the jobs section - but articles about your latest product or initiative.  Make sure the journalist adds a line about currently looking for.... and your follow up information.