Yes there is a module called mod_evasive. You can set upper limit of number of connections per ip allowed using following directive:
Code:
evasive.max-conns-per-ip = 3
However, this 1.5 specific module, so you need to run 1.5 series lighttpd which is under beta for some time.
Docs:ModEvasive - lighttpd - secure, fast, compliant, and very flexible web-server - Trac