Hi I don't know if this has been posted before if so i'm sorry to repeat it.
This site will allow you up to 60 views per day with free downloads of datasheets. To date i have not searched for one and had no results and the best thing is it's freeeee.
No restrictions on the number of downloads that I'm aware of (at least I've never run into any), no registration, etc... and it's nearly always had the datasheets I needed. It does open the datasheet in a frame, so it keeps the search bar, etc visible at the top, and keeps a panel of ads open on the right. However, (unless perhaps you're running a low monitor resolution) it's not very obtrusive at all, and you can always "save a copy" from within acrobat reader and open it locally.