SR3 had no lack of adventures, but releases reflected the trend for diminishing sales of stand-alone canned adventures. Therefore FASA and later FanPro adopted several different approaches: They introduced 3 in 1 adventure packs like
First Run,
Predator and Prey, and
Missions (this one had 4).They also offered full-fledged multiple adventure/scene campaigns in the format of the original
Harlequin with
Harlequin's Back,
Brainscan, and
Survival of the Fittest. They also introduced my favorite format though not necessarily the most popular, the "track-style" campaign books (such as
Blood in the Boardroom and
Mob War) - this format provided all the campaign context needed to run multiple adventures (ie. main NPCs, organization profiles, timeline of events, etc) but did not come with a scene-by-scene adventure breakdowns usual in canned adventures (instead introducing Adventure Frameworks that while highly customizable and easy to tweak to any campaign, require more work to bring to the table than a traditional adventure).
Shadowrun 4 will continue to release campaign books and the occassional stand-alone adventure. So far we've released a single introductory adventure
On the Run (which includes a nod to those familiar with SR2 adventures), and a campaign/setting book (similar to the tracked campaign format above) called
Emergence. Our next campaign book,
Ghost Cartels, will focus on an underworld storyline and provide a new format that combines the best elements of a traditional multi-stage campaign (like
Harlequin) and the track campaigns (like
Mob War). We are also planning on exploring canned adventures as ebooks to counter the high costs of production of canned hardcopy adventures.
Aside from all that, Catalyst supports the
SR:Missions which is launching its "third season"/campaign arc and has 25+
free adventures available (some of which can be found
here). SR:M will be getting a facelift in the coming months and future adventures in the new season will have higher production values but will no longer be free (though the ebooks will likely cost under $5).