What are the top tools to get the word out about your current vacancies ?

Social channels and networks spreads the word in seconds and as you mentioned its the most effective tool nowadays.
Postings on different networks gives company x exposure and what makes company x different from many other posts.
The way the recruiter post the vacancy or the AD and the Logo of the company/ company profile ..Etc

Using different social media networks had become an effective tool , so posting a vacancy in facebook,twitter,linked in,etc..
will for sure give exposure and prompote WOM

I have been using (URL removed due to policy violation. Please contact support for further information.) for announcing the new opening and found it very effective, reason being;

1 - Quick penetration among the candidates.

2 - Cost effective.

3 - Promote company image among followers.

4- Attracts multiple profile.

Though I also send the announcement to internal employees and do effective networking which helps to generate resume. Additionally, i also approach the "Placement Cell" of reputable universities where we have fair idea about availability of potential candidates.

Using different social media