At the 5 February 2011 CoCo Cafe in Scotland there were three topics and between 6-9 people.
The aim of the two stream schemes below were to ensure that everybody sees everybody and has visited all the three topic tables.

Scheme with table hosts
Everybody sees different people but the table hosts see only their own table/topic 

Round	Topic 1	Topic 2	Topic 3
1	abc	def	ghi
2	aei	dbh	gcf
3	afh	dci	gbe
4	The people who haven't seen each other group together.

The people are assigned letters of the alphabet.

Scheme without table hosts.
This scheme can easily be extended to accommodate 6-12 people.
If only nine two people travel all the three topics. Disadvantage is the transfer of information from table to table.

Round	Topic 1	Topic 2	Topic 3
1	abc	def	ghi
2	fgh	abi	cde
3	dei	cgh	abf
4	The people who haven't seen each other group together.