Scrum-ban

Scrumban is an agile methodology based on elements of Scrum and Kanban.

From Scrum:

• Roles: Product Owner, Team, (and other roles as needed) 
• Ceremonies/Artifacts: Daily Scrum, Task Board, Product Increment

From Kanban:

• Visual Workflow
• Just-in-Time (making what is needed, when it is needed, and only in the amount that is needed)
• Limit Work in Process (WIP)
• Optimize the process/flow

Scrum vs. Scrumban

	Scrum	Scrumban
Board/Artifacts	Board, backlogs, burndowns	Board only
Ceremonies	Daily scrum, sprint planning, sprint review, sprint retrospective	Daily scrum (planning, review and retrospective as needed)
Iterations	Yes (sprints)	No (continuous flow)
Estimation	Yes	No
Teams	Must be cross-functional	Can be specialized
Roles	PO, SM, Team	Team + needed roles
Teamwork	Collaborative as needed by task	Swarming to achieve goals
WIP	Controlled by sprint content	Controlled by workflow state
Changes	Should wait for the next sprint	Added as needed on the board (to do)
Product Backlog	List of prioritized and estimated stories	Just in time cards
Impediments	Dealt with immediately	Avoided

    Source: Dimitri Ponomareff's Scrum vs. Kanban: An Introduction to Scrumban, slide 18

Practical Tips:

• Extend board to story creation/elaboration
• Avoid creating/elaborating too many stories – (reduce waste)
• Assume the necessary level of analysis before starting development
• The backlog should be event-driven with an order point
• Prioritization on demand: the ideal work planning process should always provide the team with best thing to work on next, no more no less
• Dealing with Impediments:
• Low priority work or refactoring/personal growth/technical advancements – anything that does not create work downstream.

Is Scrumban better than Scrum?
I find that it compliments Scrum very well and is better suited for certain activities / types of work.  Depends on the nature of the work your team is and environment your working within.  Scrumban is an alternative to Scrum, that works better if your team . Depends on the type of work that your team is doing.  and that for most "planned" applications Scrum is better.
     See also: Kanban's Not Better than Scrum, It's Just Smaller

More Resources (worth reviewing)

Cory Ladas' website or Scrumban - Essays on Kanban for Lean Software Development

Henrik Kniberg and Mattias Skarin' s Kanban and Scrum: Making the most of both

David J. Anderson's: Kanban: Successful Evolutionary Change for Your Technology Business

Crisp Intro post on Kanban 

Yuval Yeret 's  Scrumban: Taking Scrum outside it's comfort zone

Dimitri Ponomareff's Scrum vs Kanban: Introduction to Scrumban