My twopenneth for what it's worth 
Electricity and Energy are both good secondaries. Both have three good attacks and endurance recovery/saving powers, electricity has the advantage of also having a very good mele range hold, but energy has a guaranteed stun (total focus) and two powers which also boost your primary. Overall, I would say energy is probably a better match although both would work.
I personally like Hover and TP or Fly for travel, but I've used the leaping pool in the past, you can make it work just fine.
Hope that helps.
IMH(AB)O, I'd say Energy and Flight.
Dev is nice, but the drone annoys the hell out of me.
Flight's Hover gives much needed defence, and Flight is just cool 
Thanks for all the help...with the Energy secondary is that mostly melee? If it is if I have hover/flight wouldn't that mean that some of my powers are wasted?
Energy secondary is split into Boosts and Melees. Hover is there for when you're in trouble.
Main attack chain should be Boost/Sonic/Sonic/Boost (melee if they're too close (Knockback will push them back into sonic).
Hover should be active if you're against a large group or need to avoid the floor.
Flight's for getting to the missions.
Excellent...thx again for the help...better get down Maplins now get and get the bits I need for my hover boots
Both energy and electricity secondary (in fact almost all the secondary powers) are mele range.
Before ED with 6 slotted hover you could get in and out of mele range depending on what was most appropriate at the time very quickly and easily. 3 slotted hover doesn't really do this. Personally I'm using hover (3 flight speed) and teleport (2 end reducers to allow combat use) on my blapper and I'm finding it very useful. I tend to open most fights at range, whether I'm soloing or teaming, but then I can quickly get in to mele (and quickly get back out again if I have to). Adding a third dimension on to your movement really can increase survivability quite a bit once you learn how to make the most of it. Even if you take mele attacks you probably wont spend all your time in mele, sometimes keeping range is very useful and hover is a good way to do it. I keep hover on all the time because it reduces knockback (instead of being knocked back, you just spin round in the air which makes it relatively harmless).
However the leaping pool also has some big advantages too. It gives you immobilisation protection in the form of combat jumping, a good travel power, and knockback plus limited hold protection from acrobatics (this protects from one hold only, you will still get held, but less so).
One thing to bear in mind is that the hover/fly or hover/TP route takes a fair amount of slotting to be effective, and it has to be SOs. In addition if you were to take either fly or TP as a travel power they're very endurance heavy, running either of those before you get stamina can be annoying. For a lower level character you might want to just take the leaping pool. You can always respec later on if you don't like it, or when you have the slots spare to make one of the other travel powers work.
Foolio! Cool name, I call my wife that all the time
i agree both energy and elec are great 2ndries. ice is great for controlling but does a bit less outright dmg and has less buffs, you will probably need stamina if you go /ice too, with energy and elec in the 2ndry you can manage quite well without stamina (got to 50 without it and can solo pretty much anything).
bear in mind that power boost from the energy set will at least double your hover speed so 3 slotted hover + PB is faster than unslotted flight, im finding 3 SOs in hover is enough to get about on considering i have range and melee on the toon in question. as for what has been said about your attack chain consisting mainly of primaries then a few secondaries, in terms of both elec and nrg, the secondary melees can 1 shot minions with aim and BU on, and have more auto control than the primaries making them far more time efficient, energy stuns like no ones business and elec sleeps and stuns and holds (both knockback too, elec has PBAoE KB tho where nrg has inreased magnitude of stun in place of it). bear in mind when worrying abotu the path of the blapper or blaptroller (blapper = blaster/scrapper btw), that power boost + sirens song will sleep the mob and u can happily 1 or 2 shot things before they wake up, if you are elec you will take the drain/hold approach most likely, both work well tho imo.
i can show you all the elec powers if you want to see them on defiant, but am away this weeekend, so feel free to PM me, can prolly hook you up with an energy blaster too if you wanted.
have fun, thats the main thing.
Plight
Thx for input everyone...I'm going to go for...
Tech/Sonic/Elec Blaster
I'm not sure on the travel power yet...but I'm tempted to take Hover just to up my defence and KB res a little. But I think I'm going to go with combat jumping to start with and see how it goes...I may respec to hover/fly at a later date.
So keep an eye out for Professor Foolio on your travels 
I'm a bit of a noob and have only been playing for a few weeks...I have had a few characters just to get the gist of it all and now want to build a blaster as my main character. However, I need a little advice...
I like the idea of Sonics and would like to find a secondary power to complement it. I mainly solo but would still like a build which could work in a team when necessary. I have a particular idea in my head for a tech/blaster so was thinking either elec/energy but am open to suggestions.
I'm also not sure which travel power to have...fly/hover looks goods as it seems to offer good protection for squishies like me but I'm not sure it would fit in with the idea I have for the character. I would prefer something ground based like SJ but would this make me easy meat at higher levels?
Anywho...thx in advance for any help received.