see this: http://wiki.mikrotik.com/wiki/Queue
and this: http://wiki.mikrotik.com/wiki/PCQ
and this: http://wiki.mikrotik.com/wiki/HTB
and this: http://wiki.mikrotik.com/wiki/Queue_Size
and this: http://forum.mikrotik.com/t/qos-best-practice-janism-document/24456/1
and this: http://forum.mikrotik.com/t/does-queue-processing-qos-pcq-htb-etc-depend-on-isp/25197/1
and this: http://forum.mikrotik.com/t/is-priority-really-working/24459/1
and this: http://luxik.cdi.cz/~devik/qos/htb/manual/userg.htm
and this: http://www.faqs.org/docs/Linux-HOWTO/ADSL-Bandwidth-Management-HOWTO.html
and this: http://www.adsl-optimizer.dk/thesis/main_final_hyper.pdf
and this: http://mum.mikrotik.com/presentations/EG07/sunday.pdf
and others…
What is your internet uplink?