Sqllite Manager Firefox Plugin
Cross Platform,Firefox. This is the sqlite Tool I've used the most. It's actually really good,especially considering it runs in a browser. It gets updated pretty frequently which is nice. There aren't (at least I can't find) keyboard shortcuts for executing queries. The UI isn't awesome,but it get's the job done. It's got decent import features,( delimited files,sql and xml). No Excel import but you can always save as a CSV file right? If you are importing a big file or querying a lot of data sometimes the script will timeout which may or may not cause issues. Usually you can opt to continue running the script and it sort's itself out eventually.

Sqlite Administrator
Windows Client,FreeWhen I need to do more in the way of writing complex queries or db design,I'll use sqlite Administrator. The query results grid is kind of weird as it tends to expand small columns so most of you data get's pushed off the side of the window. And I still have no idea what is going on with the "Edit Data" tab.

SqlSpy,Windows,Free
While it doesn't have any import features that I could find,sqlSpy looks like a nice solid query tool and it's free. This may replace sqlite Admin for me. I'm going to spend some more time with it.

SqlMaestro Windows $79 non commercial $139 commercial
This tool has a nice UI but it's really pricey. The extra tools it gives you above the free applications,like Blob Viewer,and Query build I don't really need. The Import Tool is backwards IMO. You have to create the table /before/ you could import a csv or xls file which is a PITA. That immediately disqualified it as the FF Plugin and sql Admin do a far better job at importing for free.

Sqlabs Sqlite Manager Win/Mac $49 for one or $79 for dual platform license.
I was excited when I saw,sqlabs sqlManager. It's a paid app but it has an OSX and Windows version. Both of which look really pretty UI-wise but the utility isn't there for a paid app. There are no import features I can find. When you are on the sql Editor Panel you cannot see the table list which is a fail. It's got a query builder,but I never use those things. On the plus side it has Analysis and Optimization tools which could be useful. The demo is overly limiting so it's hard to get a good feel for it.

RazorSql Windows,OS X,Linux $69.95 After taking Razor for a spin I was fairly impressed. It works with a ton of db's other than sqlite. The query editor is pretty good. The Import feature is backwards like sqlmaestro,where it won't create the imported table for you,you have to do it ahead of time. It's a cross platform java app so the UI is a little sluggish compared to a native app and has that Java look and feel to it. If I were to pay for one of these tools Razor would be it.