Increase Link Capacity with Combine Link

As long as we know link capacity is limit depend
on type of link, E1 2048 Kbps, DS3 45 Mbps etc. Sometimes we need more of link capacity use combine many link existing capacity become to big capacity.

In here I have several example to increase link capacity :

o load balancing of several link with IGP routing protocol example OSPF
o load balancing of 2 or more link with eBGP multihop use static route to reach next hop BGP peer
o combine 2 or more interface with a new logical interface use Serial interface and Ethernet interface

If you have a different way to increase link capacity without buy a new link, you can share with me. Thank you.