Before the Google Panda update Bookmarking and directory submission were pretty hot stuff and worked well to increase your SERPs. Now they only increase your web prescense and do nothing much to increase the PR of your site either.
Correction, before Panda SB'ing had begun to lose it's ranking authority up until a certain point or quantity. SB'ing was mainly used for indexing and a great first tier of links to your money site or new site.
After awhile, bookmarking lost alot of it's "oomph" and high PR profile links, mass article submission, and blog comments (high page PR, domain PR, and automated) became all the rage, even direct to money site with xrumer for link indexation and 2nd tier.
from my experience, post panda is about high quality link diversity not only in link type but also IP. With this came the resurgence of bookmarking as a very powerful link source when done right (unique content, diverse anchors, unique accounts). Panda is really just back to business as usual. We had a hay day there for awhile with some questionable tactics but we're basically back to 2008ish with better onpage SEO factors IMHO. Other viable signals I'm seeing is the popularity of your backlinks, IE, backlinking your backlinks. Yes, this has been in play for awhile but I'm seeing, from results, as being more powerful than indexation was last year at this time. I think the name of the game is "popularity" from a diverse perspective, bookmarking is a great way for G to gauge popularity of a site, hence the suppsed upcoming rollout of "social signals". Social=popularity from diverse "trusted" sources. Mix that in with high PR directs and you have yourself a panda slayer.