256GB SSD -> OS + all applications + steam + most used VMs + http downloads
1TB HDD -> All multimedia (video+audio+photos) + backups + installation files + torrent downloads + less used experimental VMs
I only sometimes move Virtual Machines and some installation files between the two. If your SSD is large enough for your needs (256 or 512 in my case) then you won't need to move files around.
There are some cache SSDs available from various sources with 32GB and more capacity, but they are usually tied to Windows and can't be used on other OSs.