Celery like software for Ruby?

There are a lot of options for queues in ruby.

Sidekiq -> https://github.com/mperham/sidekiq
Resque, you got the link
DelayedJob -> http://blog.leetsoft.com/delayed_job/

All of them are pretty much the same. So you just need to use the one you are more confortable working with the examples.
In my projects i ended up using Sidekiq, the reviews about it are pretty awesome.

Here is a good comparison of Resque and Sidekiq. Resque vs Sidekiq?

Sidekiq uses threads so there is a much lower memory footprint then Resque or delayed job. the downside, and a huge one i think, is your workers MUST be thread safe, including whatever gems you use in them. vetting all the code that goes into workers for thread safety is a on-taking for sure, as is potentially debugging contention in lower level libs, seg faults, etc..