The following links connect you to critical appraisal tools for resources that summarize multiple studies.
Clinical Practice Guidelines Appraisal Tool
AGREE II Instrument - The Appraisal of Guidelines for Research and Evaluation (AGREE) Instrument addresses the quality of practice guidelines.
Additional Tools for Synthesized Reports
the NNT - Brief summaries of NNT “Number-Needed-to-Treat” based on critical appraisal of systematic reviews related to therapy or diagnosis studies.
EvidenceUpdates - Access to articles from over 110 clinical journals that have been critically appraised by a panel of practicing physicians. Includes a searchable database and email alerts option. From BMJ Publishing Group and McMaster University's Health Information Research Unit.