i found some modules for feed parsing(aggregator,feeds,feedapi). i am confusing to choose right one. i need to filter and classify the feeds. can any one guide me
Feeds is an attempt to replace FeedAPI, done by the same developers. It should be better, but as FeedAPI has gathered some extensions by other modules, Feeds might not offer some features yet that where available via extension modules before (note that this is just speculation).
Both offer more functionality than Drupals build in Aggregator module, which is geared towards a 'lightweight' aggregation approach.
So I would start with checking the built in Aggregator module. It offers 'categorization' of feeds and items, which might be enough for your need to 'filter' and 'classify'. If it is not enough, I would check the new Feeds module next, and only 'fall back' to FeedsAPI, if you need some extension/functioanlity not available for Feeds yet.