There are loads of job sites these days. I’m not going to list them all, that’s what Google is for. The below job sites are specifically for design positions, and where you can find postings from good studios and agencies country-wide.
A few of the big magazine names (Design Week, Creative Review) also have job sections, but they tend to be a bit more London centric. From experience, the more generic the job site (Reed, Monster) the worst the job. Not always, but it’s what we’ve come to notice. In the past we’ve posted our positions on ifyoucouldjobs.
Twitter and Instagram are good places to keep an eye on the latest job openings. Maybe Facebook, but neither of us use it so that’d be a guess. Start following all those studios you admire, and get searching tags to find them. We’ve always made a big song and dance on social when advertising for a designer, and I can’t see that trend ever stopping.
Personally I’ve never used a recruiter. Dave has, and went for an interview at a Sheffield agency soon after leaving College, so they can work. Craft are a creative and design specific recruiter. We’ve never used them, but heard nice things.
Occasionally you’ll hear about an opening before it’s public knowledge. But to do that you need to be connected. And to do that you need to start talking to people, so go and read this about building relationships if you haven’t already.