Answering a question on ways to hide layers in groups in the After effects timeline, Todd Kopriva mentioned that Show and hide layers in the Timeline panel in AE Help had some suggestions, including Zorro-The Layer Tagger, a script from Lloyd Alvarez. Todd noted that you could also:
"add comments to layers and then use the filtering/searching in the Timeline panel to show and hide layers according to these tags."
[update: Roland Kahlenberg adds, "The Timeline has a Label Column that allows you to group your layers. You can then select a particular group with the Select Label Group option available via right-click contextual option. Then it's a matter of Shy or Hide the selected layers."]
Also, while there is no master override Solo button in the timeline, you can also use Zorro-The Layer Tagger turn everything on to spot check a comp quick. Zorro lets you
make selection and isolation sets by adding comment tags to layers, and new for CS5 is layer color label support. Here's the demo:
Chris & Trish Meyer's series of tips, tricks, gotchas, factoids, and shortcuts continues with tips on layers in CMG Hidden Gems: Chapter 7 – Trimming Layers. AdobeAE added supporting AE Help links for trimming and slip-editing layers, splitting layers, Sequence Layers keyframe assistant.