If you are an author who is looking to get speaking engagements or commissions you can register with an organisation called Contact An Author. For an annual fee (£45) you can go on their database. You create a web page, which gives background information and states your availability for interviews, events and writing work.
For more information visit: Contact an Author.
In addition, there is The Society of Authors database.
You will need to read the eligibility criteria for joining. Membership is £90.00 per year (£64 if you are under 35) and your subscription entitles you to advice on all aspects of the writing profession, including confidential clause-by-clause vetting of any contract you are offered from a publisher, agent, producer, etc. It also entitles you to be on their searchable database.
Here is an example of my entry on the Society of Authors database. The profile of author Pauline Rowson
In addition you can advertise on your own web site or blog.