connecting 2 UNOs

just wondering if there are any usefull projects using 2 UNOs .from what i read they are mostly simple master and slave ideas ,but need something more complex , meaty and involved .

Why don't you tell us what your "meaty, complex, involved" project is. When it comes to making two Arduinos communicate, each message is handled separately, which is pretty simple.

Im currently working on an RS485 connection between arduinos
see
Arduino RS485 communication for home automation project - under networking on this forum
Im using a PC as a host to communicate with a master which in turn will communicate with up to 32 slave devices/arduinos
see Nick gammons page

J.

The Big Bagpipe has a number of arduinos connected together http://www.thebigbagpipe.com/home/concept

At one time there was a "dual core" DIY Drone http://diydrones.com/profiles/blog/show?id=705844:BlogPost:40459

Someone also made an "ExtraCore library for Arduino" Dual Core Arduino For More Pins | Hackaday

knuckles:
just wondering if there are any usefull projects using 2 UNOs .from what i read they are mostly simple master and slave ideas ,but need something more complex , meaty and involved .

You could use I2C:

You can make either one the master (not at the same time of course). You could "broadcast" to multiple slaves.